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441 KiB

Open AccessArticle

Molecular Dynamics of Neutral Polymer Bonding Agent (NPBA) as Revealed by Solid-State NMR Spectroscopy

by Wei Hu, Yongchao Su, Lei Zhou, Aimin Pang, Rulin Cai, Xingang Ma and Shenhui Li

Molecules 2014, 19(1), 1353-1366; https://doi.org/10.3390/molecules19011353 - 22 Jan 2014

Cited by 8 | Viewed by 8593

Abstract

Neutral polymer bonding agent (NPBA) is one of the most promising polymeric materials, widely used in nitrate ester plasticized polyether (NEPE) propellant as bonding agent. The structure and dynamics of NPBA under different conditions of temperatures and sample processing are comprehensively investigated by [...] Read more.

Neutral polymer bonding agent (NPBA) is one of the most promising polymeric materials, widely used in nitrate ester plasticized polyether (NEPE) propellant as bonding agent. The structure and dynamics of NPBA under different conditions of temperatures and sample processing are comprehensively investigated by solid state NMR (SSNMR). The results indicate that both the main chain and side chain of NPBA are quite rigid below its glass transition temperature (T_g). In contrast, above the T_g, the main chain remains relatively immobilized, while the side chains become highly flexible, which presumably weakens the interaction between bonding agent and the binder or oxidant fillers and in turn destabilizes the high modulus layer formed around the oxidant fillers. In addition, no obvious variation is found for the microstructure of NPBA upon aging treatment or soaking with acetone. These experimental results provide useful insights for understanding the structural properties of NPBA and its interaction with other constituents of solid composite propellants under different processing and working conditions. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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686 KiB

Open AccessArticle

A STD-NMR Study of the Interaction of the Anabaena Ferredoxin-NADP⁺ Reductase with the Coenzyme

by Lara V. Antonini, José R. Peregrina, Jesús Angulo, Milagros Medina and Pedro M. Nieto

Molecules 2014, 19(1), 672-685; https://doi.org/10.3390/molecules19010672 - 7 Jan 2014

Cited by 1 | Viewed by 7745

Abstract

Ferredoxin-NADP⁺ reductase (FNR) catalyzes the electron transfer from ferredoxin to NADP⁺ via its flavin FAD cofactor. To get further insights in the architecture of the transient complexes produced during the hydride transfer event between the enzyme and the NADP⁺ coenzyme [...] Read more.

Ferredoxin-NADP⁺ reductase (FNR) catalyzes the electron transfer from ferredoxin to NADP⁺ via its flavin FAD cofactor. To get further insights in the architecture of the transient complexes produced during the hydride transfer event between the enzyme and the NADP⁺ coenzyme we have applied NMR spectroscopy using Saturation Transfer Difference (STD) techniques to analyze the interaction between FNR_ox and the oxidized state of its NADP⁺ coenzyme. We have found that STD NMR, together with the use of selected mutations on FNR and of the non-FNR reacting coenzyme analogue NAD⁺, are appropriate tools to provide further information about the the interaction epitope. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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3029 KiB

Open AccessArticle

Solution Structure of the Circular γ-Domain Analog from the Wheat Metallothionein E_c-1

by Katsiaryna Tarasava, Silke Johannsen and Eva Freisinger

Molecules 2013, 18(11), 14414-14429; https://doi.org/10.3390/molecules181114414 - 21 Nov 2013

Cited by 8 | Viewed by 6026

Abstract

The first cyclic analog of a metallothionein (MT) was prepared and analyzed by UV and (magnetic) circular dichroism spectroscopy, ESI-MS as well as NMR spectroscopy. Results reveal that the evaluated cyclic g-E_c-1 domain of the wheat MT E_c-1 retains [...] Read more.

The first cyclic analog of a metallothionein (MT) was prepared and analyzed by UV and (magnetic) circular dichroism spectroscopy, ESI-MS as well as NMR spectroscopy. Results reveal that the evaluated cyclic g-E_c-1 domain of the wheat MT E_c-1 retains its ability to coordinate two Zn(II) or Cd(II) ions and adopts a three-dimensional structure that is highly similar to the one of the linear wild-type form. However, the reduced flexibility of the protein backbone facilitates structure solution significantly and results in a certain stabilization of metal binding to the protein. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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2817 KiB

Open AccessArticle

The Clip-Segment of the von Willebrand Domain 1 of the BMP Modulator Protein Crossveinless 2 Is Preformed

by Juliane E. Fiebig, Stella E. Weidauer, Li-Yan Qiu, Markus Bauer, Peter Schmieder, Monika Beerbaum, Jin-Li Zhang, Hartmut Oschkinat, Walter Sebald and Thomas D. Mueller

Molecules 2013, 18(10), 11658-11682; https://doi.org/10.3390/molecules181011658 - 25 Sep 2013

Cited by 10 | Viewed by 8908

Abstract

Bone Morphogenetic Proteins (BMPs) are secreted protein hormones that act as morphogens and exert essential roles during embryonic development of tissues and organs. Signaling by BMPs occurs via hetero-oligomerization of two types of serine/threonine kinase transmembrane receptors. Due to the small number of [...] Read more.

Bone Morphogenetic Proteins (BMPs) are secreted protein hormones that act as morphogens and exert essential roles during embryonic development of tissues and organs. Signaling by BMPs occurs via hetero-oligomerization of two types of serine/threonine kinase transmembrane receptors. Due to the small number of available receptors for a large number of BMP ligands ligand-receptor promiscuity presents an evident problem requiring additional regulatory mechanisms for ligand-specific signaling. Such additional regulation is achieved through a plethora of extracellular antagonists, among them members of the Chordin superfamily, that modulate BMP signaling activity by binding. The key-element in Chordin-related antagonists for interacting with BMPs is the von Willebrand type C (VWC) module, which is a small domain of about 50 to 60 residues occurring in many different proteins. Although a structure of the VWC domain of the Chordin-member Crossveinless 2 (CV2) bound to BMP-2 has been determined by X-ray crystallography, the molecular mechanism by which the VWC domain binds BMPs has remained unclear. Here we present the NMR structure of the Danio rerio CV2 VWC1 domain in its unbound state showing that the key features for high affinity binding to BMP-2 is a pre-oriented peptide loop. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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907 KiB

Open AccessArticle

Probing the Residual Structure in Avian Prion Hexarepeats by CD, NMR and MD Techniques

by Luigi Russo, Luca Raiola, Maria Anna Campitiello, Antonio Magrì, Roberto Fattorusso, Gaetano Malgieri, Giuseppe Pappalardo, Diego La Mendola and Carla Isernia

Molecules 2013, 18(9), 11467-11484; https://doi.org/10.3390/molecules180911467 - 16 Sep 2013

Cited by 8 | Viewed by 6929

Abstract

Many proteins perform essential biological functions by means of regions that lacking specific organized structure exist as an ensemble of interconverting transient conformers. The characterization of such regions, including the description of their structural propensities, number of conformations and relative populations can provide [...] Read more.

Many proteins perform essential biological functions by means of regions that lacking specific organized structure exist as an ensemble of interconverting transient conformers. The characterization of such regions, including the description of their structural propensities, number of conformations and relative populations can provide useful insights. Prion diseases result from the conversion of a normal glycoprotein into a misfolded pathogenic isoform. The structures of mammal and chicken prion proteins show a similar fold with a globular domain and a flexible N-terminal portion that contains different repeated regions: octarepeats (PHGGGWGQ) in mammals and hexarepeats (PHNPGY) in chickens. The higher number of prolines in the hexarepeat region suggests that this region may retain a significant amount of residual secondary structure. Here, we report the CD, NMR and MD characterization of a peptide (2-HexaPY) composed of two hexarepeats. We combine experimental NMR data and MD to investigate at atomic level its ensemble-averaged structural properties, demonstrating how each residue of both repeats has a different quantified PPII propensity that shows a periodicity along the sequence. This feature explains the absence of cooperativity to stabilize a PPII conformation. Nonetheless, such residual structure can play a role in nucleating local structural transitions as well as modulating intra-molecular or inter-molecular interactions. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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Open AccessArticle

Protein Structure Validation and Identification from Unassigned Residual Dipolar Coupling Data Using 2D-PDPA

by Arjang Fahim, Rishi Mukhopadhyay, Ryan Yandle, James H. Prestegard and Homayoun Valafar

Molecules 2013, 18(9), 10162-10188; https://doi.org/10.3390/molecules180910162 - 22 Aug 2013

Cited by 5 | Viewed by 7519

Abstract

More than 90% of protein structures submitted to the PDB each year are homologous to some previously characterized protein structure. The extensive resources that are required for structural characterization of proteins can be justified for the 10% of the novel structures, but not [...] Read more.

More than 90% of protein structures submitted to the PDB each year are homologous to some previously characterized protein structure. The extensive resources that are required for structural characterization of proteins can be justified for the 10% of the novel structures, but not for the remaining 90%. This report presents the 2D-PDPA method, which utilizes unassigned residual dipolar coupling in order to address the economics of structure determination of routine proteins by reducing the data acquisition and processing time. 2D-PDPA has been demonstrated to successfully identify the correct structure of an array of proteins that range from 46 to 445 residues in size from a library of 619 decoy structures by using unassigned simulated RDC data. When using experimental data, 2D-PDPA successfully identified the correct NMR structures from the same library of decoy structures. In addition, the most homologous X-ray structure was also identified as the second best structural candidate. Finally, success of 2D-PDPA in identifying and evaluating the most appropriate structure from a set of computationally predicted structures in the case of a previously uncharacterized protein Pf2048.1 has been demonstrated. This protein exhibits less than 20% sequence identity to any protein with known structure and therefore presents a compelling and practical application of our proposed work. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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840 KiB

Open AccessArticle

NMR Study on the Interaction of Trehalose with Lactose and Its Effect on the Hydrogen Bond Interaction in Lactose

by Eric Morssing Vilén and Corine Sandström

Molecules 2013, 18(8), 9735-9754; https://doi.org/10.3390/molecules18089735 - 14 Aug 2013

Cited by 12 | Viewed by 8794

Abstract

Trehalose, a well-known stress-protector of biomolecules, has been investigated for its effect on the mobility, hydration and hydrogen bond interaction of lactose using diffusion-ordered NMR spectroscopy and NMR of hydroxy protons. In ternary mixtures of trehalose, lactose and water, the two sugars have [...] Read more.

Trehalose, a well-known stress-protector of biomolecules, has been investigated for its effect on the mobility, hydration and hydrogen bond interaction of lactose using diffusion-ordered NMR spectroscopy and NMR of hydroxy protons. In ternary mixtures of trehalose, lactose and water, the two sugars have the same rate of diffusion. The chemical shifts, temperature coefficients, vicinal coupling constants and ROE of the hydroxy protons in trehalose, lactose and sucrose were measured for the disaccharides alone in water/acetone-d₆ solutions as well as in mixtures. The data indicated that addition of trehalose did not change significantly the strength of the hydrogen bond interaction between GlcOH3 and GalO5' in lactose. Small upfield shifts were however measured for all hydroxy protons when the sugar concentration was increased. The chemical shift of the GlcOH3 signal in lactose showed less change, attributed to the spatial proximity to GalO5'. Chemical exchange between hydroxy protons of lactose and trehalose was observed in the ROESY NMR spectra. Similar effects were observed with sucrose indicating no specific effect of trehalose at the concentrations investigated (73 to 763 mg/mL) and suggesting that it is the concentration of hydroxy groups more than the type of sugars which is guiding intermolecular interactions. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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Open AccessArticle

Accidental Interaction between PDZ Domains and Diclofenac Revealed by NMR-Assisted Virtual Screening

by Takeshi Tenno, Natsuko Goda, Yoshitaka Umetsu, Motonori Ota, Kengo Kinoshita and Hidekazu Hiroaki

Molecules 2013, 18(8), 9567-9581; https://doi.org/10.3390/molecules18089567 - 9 Aug 2013

Cited by 9 | Viewed by 7028

Abstract

In silico approaches have become indispensable for drug discovery as well as drug repositioning and adverse effect prediction. We have developed the eF-seek program to predict protein–ligand interactions based on the surface structure of proteins using a clique search algorithm. We have also [...] Read more.

In silico approaches have become indispensable for drug discovery as well as drug repositioning and adverse effect prediction. We have developed the eF-seek program to predict protein–ligand interactions based on the surface structure of proteins using a clique search algorithm. We have also developed a special protein structure prediction pipeline and accumulated predicted 3D models in the Structural Atlas of the Human Genome (SAHG) database. Using this database, genome-wide prediction of non-peptide ligands for proteins in the human genome was performed, and a subset of predicted interactions including 14 PDZ domains was then confirmed by NMR titration. Surprisingly, diclofenac, a non-steroidal anti-inflammatory drug, was found to be a non-peptide PDZ domain ligand, which bound to 5 of 15 tested PDZ domains. The critical residues for the PDZ–diclofenac interaction were also determined. Pharmacological implications of the accidental PDZ–diclofenac interaction are further discussed. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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1616 KiB

Open AccessArticle

Solid-, Solution-, and Gas-state NMR Monitoring of ¹³C-Cellulose Degradation in an Anaerobic Microbial Ecosystem

by Akira Yamazawa, Tomohiro Iikura, Amiu Shino, Yasuhiro Date and Jun Kikuchi

Molecules 2013, 18(8), 9021-9033; https://doi.org/10.3390/molecules18089021 - 29 Jul 2013

Cited by 33 | Viewed by 8690

Abstract

Anaerobic digestion of biomacromolecules in various microbial ecosystems is influenced by the variations in types, qualities, and quantities of chemical components. Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for characterizing the degradation of solids to gases in anaerobic digestion processes. Here [...] Read more.

Anaerobic digestion of biomacromolecules in various microbial ecosystems is influenced by the variations in types, qualities, and quantities of chemical components. Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for characterizing the degradation of solids to gases in anaerobic digestion processes. Here we describe a characterization strategy using NMR spectroscopy for targeting the input solid insoluble biomass, catabolized soluble metabolites, and produced gases. ¹³C-labeled cellulose produced by Gluconacetobacter xylinus was added as a substrate to stirred tank reactors and gradually degraded for 120 h. The time-course variations in structural heterogeneity of cellulose catabolism were determined using solid-state NMR, and soluble metabolites produced by cellulose degradation were monitored using solution-state NMR. In particular, cooperative changes between the solid NMR signal and ¹³C-¹³C/¹³C-¹²C isotopomers in the microbial degradation of ¹³C-cellulose were revealed by a correlation heat map. The triple phase NMR measurements demonstrated that cellulose was anaerobically degraded, fermented, and converted to methane gas from organic acids such as acetic acid and butyric acid. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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1686 KiB

Open AccessArticle

NMR Solution Structure of a Chymotrypsin Inhibitor from the Taiwan Cobra Naja naja atra

by Yi-Jan Lin, Teppei Ikeya, Peter Güntert and Long-Sen Chang

Molecules 2013, 18(8), 8906-8918; https://doi.org/10.3390/molecules18088906 - 26 Jul 2013

Cited by 3 | Viewed by 7025

Abstract

The Taiwan cobra (Naja naja atra) chymotrypsin inhibitor (NACI) consists of 57 amino acids and is related to other Kunitz-type inhibitors such as bovine pancreatic trypsin inhibitor (BPTI) and Bungarus fasciatus fraction IX (BF9), another chymotrypsin inhibitor. Here we present the [...] Read more.

The Taiwan cobra (Naja naja atra) chymotrypsin inhibitor (NACI) consists of 57 amino acids and is related to other Kunitz-type inhibitors such as bovine pancreatic trypsin inhibitor (BPTI) and Bungarus fasciatus fraction IX (BF9), another chymotrypsin inhibitor. Here we present the solution structure of NACI. We determined the NMR structure of NACI with a root-mean-square deviation of 0.37 Å for the backbone atoms and 0.73 Å for the heavy atoms on the basis of 1,075 upper distance limits derived from NOE peaks measured in its NOESY spectra. To investigate the structural characteristics of NACI, we compared the three-dimensional structure of NACI with BPTI and BF9. The structure of the NACI protein comprises one 3₁₀-helix, one α-helix and one double-stranded antiparallel β-sheet, which is comparable with the secondary structures in BPTI and BF9. The RMSD value between the mean structures is 1.09 Å between NACI and BPTI and 1.27 Å between NACI and BF9. In addition to similar secondary and tertiary structure, NACI might possess similar types of protein conformational fluctuations as reported in BPTI, such as Cys14–Cys38 disulfide bond isomerization, based on line broadening of resonances from residues which are mainly confined to a region around the Cys14–Cys38 disulfide bond. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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1553 KiB

Open AccessArticle

Structure of the C-terminal Region of the Frizzled Receptor 1 in Detergent Micelles

by Shovanlal Gayen, Qingxin Li, Young Mee Kim and CongBao Kang

Molecules 2013, 18(7), 8579-8590; https://doi.org/10.3390/molecules18078579 - 22 Jul 2013

Cited by 13 | Viewed by 6695

Abstract

The C-terminal domains of the Frizzleds (FZDs) contain a short conserved motif (KTXXXW). It has been demonstrated that FZDs interacted with the PDZ domain of the cytoplasmic proteins such as Dishevelled through this motif and mutations in this motif disrupted Wnt/β-catenin signaling. We [...] Read more.

The C-terminal domains of the Frizzleds (FZDs) contain a short conserved motif (KTXXXW). It has been demonstrated that FZDs interacted with the PDZ domain of the cytoplasmic proteins such as Dishevelled through this motif and mutations in this motif disrupted Wnt/β-catenin signaling. We carried out structural studies for a peptide derived from the C-terminal domain of the FZD₁ in different solvents using circular dichroism and solution NMR spectroscopy. Our results showed that this domain was unstructured in an aqueous solution and formed a helical structure in detergent micelles. Fluorescence studies suggested that the tryptophan residue (W630) in the motif interacted with micelles. The solution structure of the peptide in sodium dodecyl sulfate micelles was determined and an amphipathic helix was identified. This helix may have similar function to the helix 8 of other G protein-coupled receptors. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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1489 KiB

Open AccessArticle

Application of Reductive ¹³C-Methylation of Lysines to Enhance the Sensitivity of Conventional NMR Methods

by Tanmay S. Chavan, Sherwin Abraham and Vadim Gaponenko

Molecules 2013, 18(6), 7103-7119; https://doi.org/10.3390/molecules18067103 - 18 Jun 2013

Cited by 20 | Viewed by 6737

Abstract

NMR is commonly used to investigate macromolecular interactions. However, sensitivity problems hamper its use for studying such interactions at low physiologically relevant concentrations. At high concentrations, proteins or peptides tend to aggregate. In order to overcome this problem, we make use of reductive [...] Read more.

NMR is commonly used to investigate macromolecular interactions. However, sensitivity problems hamper its use for studying such interactions at low physiologically relevant concentrations. At high concentrations, proteins or peptides tend to aggregate. In order to overcome this problem, we make use of reductive ¹³C-methylation to study protein interactions at low micromolar concentrations. Methyl groups in dimethyl lysines are degenerate with one ¹³CH₃ signal arising from two carbons and six protons, as compared to one carbon and three protons in aliphatic amino acids. The improved sensitivity allows us to study protein-protein or protein-peptide interactions at very low micromolar concentrations. We demonstrate the utility of this method by studying the interaction between the post-translationally lipidated hypervariable region of a human proto-oncogenic GTPase K-Ras and a calcium sensor protein calmodulin. Calmodulin specifically binds K-Ras and modulates its downstream signaling. This binding specificity is attributed to the unique lipidated hypervariable region of K-Ras. At low micromolar concentrations, the post-translationally modified hypervariable region of K-Ras aggregates and binds calmodulin in a non-specific manner, hence conventional NMR techniques cannot be used for studying this interaction, however, upon reductively methylating the lysines of calmodulin, we detected signals of the lipidated hypervariable region of K-Ras at physiologically relevant nanomolar concentrations. Thus, we utilize ¹³C-reductive methylation of lysines to enhance the sensitivity of conventional NMR methods for studying protein interactions at low concentrations. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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422 KiB

Open AccessArticle

Structural Characterization by NMR of a Double Phosphorylated Chimeric Peptide Vaccine for Treatment of Alzheimer’s Disease

by Karla Ramírez-Gualito, Monique Richter, Manolis Matzapetakis, David Singer and Stefan Berger

Molecules 2013, 18(5), 4929-4941; https://doi.org/10.3390/molecules18054929 - 26 Apr 2013

Viewed by 7373

Abstract

Rational design of peptide vaccines becomes important for the treatment of some diseases such as Alzheimer’s disease (AD) and related disorders. In this study, as part of a larger effort to explore correlations of structure and activity, we attempt to characterize the doubly [...] Read more.

Rational design of peptide vaccines becomes important for the treatment of some diseases such as Alzheimer’s disease (AD) and related disorders. In this study, as part of a larger effort to explore correlations of structure and activity, we attempt to characterize the doubly phosphorylated chimeric peptide vaccine targeting a hyperphosphorylated epitope of the Tau protein. The 28-mer linear chimeric peptide consists of the double phosphorylated B cell epitope Tau_229-237[pThr231/pSer235] and the immunomodulatory T cell epitope Ag85B_241-255 originating from the well-known antigen Ag85B of the Mycobacterium tuberculosis, linked by a four amino acid sequence -GPSL-. NMR chemical shift analysis of our construct demonstrated that the synthesized peptide is essentially unfolded with a tendency to form a β-turn due to the linker. In conclusion, the -GPSL- unit presumably connects the two parts of the vaccine without transferring any structural information from one part to the other. Therefore, the double phosphorylated epitope of the Tau peptide is flexible and accessible. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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Review

Jump to: Research

588 KiB

Open AccessReview

NMR Study on Small Proteins from Helicobacter pylori for Antibiotic Target Discovery: A Review

by Su-Jin Kang, Do-Hee Kim and Bong-Jin Lee

Molecules 2013, 18(11), 13410-13424; https://doi.org/10.3390/molecules181113410 - 30 Oct 2013

Cited by 4 | Viewed by 5556

Abstract

Due to the widespread and increasing appearance of antibiotic resistance, a new strategy is needed for developing novel antibiotics. Especially, there are no specific antibiotics for Helicobacter pylori (H. pylori). H. pylori are bacteria that live in the stomach and [...] Read more.

Due to the widespread and increasing appearance of antibiotic resistance, a new strategy is needed for developing novel antibiotics. Especially, there are no specific antibiotics for Helicobacter pylori (H. pylori). H. pylori are bacteria that live in the stomach and are related to many serious gastric problems such as peptic ulcers, chronic gastritis, mucosa-associated lymphoid tissue lymphoma, and gastric cancer. Because of its importance as a human pathogen, it’s worth studying the structure and function of the proteins from H. pylori. After the sequencing of the H. pylori strain 26695 in 1997, more than 1,600 genes were identified from H. pylori. Until now, the structures of 334 proteins from H. pylori have been determined. Among them, 309 structures were determined by X-ray crystallography and 25 structures by Nuclear Magnetic Resonance (NMR), respectively. Overall, the structures of large proteins were determined by X-ray crystallography and those of small proteins by NMR. In our lab, we have studied the structural and functional characteristics of small proteins from H. pylori. In this review, 25 NMR structures of H. pylori proteins will be introduced and their structure-function relationships will be discussed. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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751 KiB

Open AccessReview

The Involvement of Amino Acid Side Chains in Shielding the Nickel Coordination Site: An NMR Study

by Serenella Medici, Massimiliano Peana, Valeria Marina Nurchi and Maria Antonietta Zoroddu

Molecules 2013, 18(10), 12396-12414; https://doi.org/10.3390/molecules181012396 - 8 Oct 2013

Cited by 19 | Viewed by 6844

Abstract

Coordination of proteins and peptides to metal ions is known to affect their properties, often by a change in their structural organization. Side chains of the residues directly involved in metal binding or very close to the coordination centre may arrange themselves around [...] Read more.

Coordination of proteins and peptides to metal ions is known to affect their properties, often by a change in their structural organization. Side chains of the residues directly involved in metal binding or very close to the coordination centre may arrange themselves around it, in such a way that they can, for instance, disrupt the protein functions or stabilize a metal complex by shielding it from the attack of water or other small molecules. The conformation of these side chains may be crucial to different biological or toxic processes. In our research we have encountered such behaviour in several cases, leading to interesting results for our purposes. Here we give an overview on the structural changes involving peptide side chains induced by Ni(II) coordination. In this paper we deal with a number of peptides, deriving from proteins containing one or more metal coordinating sites, which have been studied through a series of NMR experiments in their structural changes caused by Ni(II) complexation. Several peptides have been included in the study: short sequences from serum albumin (HSA), Des-Angiotensinogen, the 30-amino acid tail of histone H4, some fragments from histone H2A and H2B, the initial fragment of human protamine HP2 and selected fragments from prion and Cap43 proteins. NMR was the election technique for gathering structural information. Experiments performed for this purpose included 1D ¹H and ¹³C, and 2D HSQC, COSY, TOCSY, NOESY and ROESY acquisitions, which allowed the calculation of the Ni(II) complexes structural models. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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665 KiB

Open AccessReview

Measuring Dynamic and Kinetic Information in the Previously Inaccessible Supra-t_c Window of Nanoseconds to Microseconds by Solution NMR Spectroscopy

by David Ban, T. Michael Sabo, Christian Griesinger and Donghan Lee

Molecules 2013, 18(10), 11904-11937; https://doi.org/10.3390/molecules181011904 - 26 Sep 2013

Cited by 32 | Viewed by 8028

Abstract

Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool that has enabled experimentalists to characterize molecular dynamics and kinetics spanning a wide range of time-scales from picoseconds to days. This review focuses on addressing the previously inaccessible supra-τ_c window (defined as τ [...] Read more.

Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool that has enabled experimentalists to characterize molecular dynamics and kinetics spanning a wide range of time-scales from picoseconds to days. This review focuses on addressing the previously inaccessible supra-τ_c window (defined as τ_c < supra-τ_c < 40 μs; in which τ_c is the overall tumbling time of a molecule) from the perspective of local inter-nuclear vector dynamics extracted from residual dipolar couplings (RDCs) and from the perspective of conformational exchange captured by relaxation dispersion measurements (RD). The goal of the first section is to present a detailed analysis of how to extract protein dynamics encoded in RDCs and how to relate this information to protein functionality within the previously inaccessible supra-τ_c window. In the second section, the current state of the art for RD is analyzed, as well as the considerable progress toward pushing the sensitivity of RD further into the supra-τ_c scale by up to a factor of two (motion up to 25 ms). From the data obtained with these techniques and methodology, the importance of the supra-τ _c scale for protein function and molecular recognition is becoming increasingly clearer as the connection between motion on the supra-τ_c scale and protein functionality from the experimental side is further strengthened with results from molecular dynamics simulations. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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Open AccessReview

Nuclear Magnetic Resonance Approaches in the Study of 2-Oxo Acid Dehydrogenase Multienzyme Complexes—A Literature Review

by Sowmini Kumaran, Mulchand S. Patel and Frank Jordan

Molecules 2013, 18(10), 11873-11903; https://doi.org/10.3390/molecules181011873 - 26 Sep 2013

Cited by 10 | Viewed by 7952

Abstract

The 2-oxoacid dehydrogenase complexes (ODHc) consist of multiple copies of three enzyme components: E1, a 2-oxoacid decarboxylase; E2, dihydrolipoyl acyl-transferase; and E3, dihydrolipoyl dehydrogenase, that together catalyze the oxidative decarboxylation of 2-oxoacids, in the presence of thiamin diphosphate (ThDP), coenzyme A (CoA), Mg [...] Read more.

The 2-oxoacid dehydrogenase complexes (ODHc) consist of multiple copies of three enzyme components: E1, a 2-oxoacid decarboxylase; E2, dihydrolipoyl acyl-transferase; and E3, dihydrolipoyl dehydrogenase, that together catalyze the oxidative decarboxylation of 2-oxoacids, in the presence of thiamin diphosphate (ThDP), coenzyme A (CoA), Mg²⁺ and NAD⁺, to generate CO₂, NADH and the corresponding acyl-CoA. The structural scaffold of the complex is provided by E2, with E1 and E3 bound around the periphery. The three principal members of the family are pyruvate dehydrogenase (PDHc), 2-oxoglutarate dehydrogenase (OGDHc) and branched-chain 2-oxo acid dehydrogenase (BCKDHc). In this review, we report application of NMR-based approaches to both mechanistic and structural issues concerning these complexes. These studies revealed the nature and reactivity of transient intermediates on the enzymatic pathway and provided site-specific information on the architecture and binding specificity of the domain interfaces using solubilized truncated domain constructs of the multi-domain E2 component in its interactions with the E1 and E3 components. Where studied, NMR has also provided information about mobile loops and the possible relationship of mobility and catalysis. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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Open AccessReview

Revealing the Properties of Plant Defensins through Dynamics

by Ana Paula Valente, Viviane Silva De Paula and Fabio C. L. Almeida

Molecules 2013, 18(9), 11311-11326; https://doi.org/10.3390/molecules180911311 - 13 Sep 2013

Cited by 20 | Viewed by 6419

Abstract

Defensins are potent, ancient natural antibiotics that are present in organisms ranging from lower organisms to humans. Although the structures of several defensins have been well characterized, the dynamics of only a few have been studied. This review discusses the diverse dynamics of [...] Read more.

Defensins are potent, ancient natural antibiotics that are present in organisms ranging from lower organisms to humans. Although the structures of several defensins have been well characterized, the dynamics of only a few have been studied. This review discusses the diverse dynamics of two plant defensins for which the structure and dynamics have been characterized, both in the free state and in the presence of target membranes. Multiple motions are observed in loops and in secondary structure elements and may be related to twisting or breathing of the α-helix and β-sheet. This complex behavior is altered in the presence of an interface and is responsive to the presence of the putative target. The stages of membrane recognition and disruption can be mapped over a large time scale range, demonstrating that defensins in solution exist as an ensemble of different conformations, a subset of which is selected upon membrane binding. Therefore, studies on the dynamics have revealed that defensins interact with membranes through a mechanism of conformational selection. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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Structural Characterization of Intrinsically Disordered Proteins by NMR Spectroscopy

by Simone Kosol, Sara Contreras-Martos, Cesyen Cedeño and Peter Tompa

Molecules 2013, 18(9), 10802-10828; https://doi.org/10.3390/molecules180910802 - 4 Sep 2013

Cited by 142 | Viewed by 17085

Abstract

Recent advances in NMR methodology and techniques allow the structural investigation of biomolecules of increasing size with atomic resolution. NMR spectroscopy is especially well-suited for the study of intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) which are in general highly flexible [...] Read more.

Recent advances in NMR methodology and techniques allow the structural investigation of biomolecules of increasing size with atomic resolution. NMR spectroscopy is especially well-suited for the study of intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) which are in general highly flexible and do not have a well-defined secondary or tertiary structure under functional conditions. In the last decade, the important role of IDPs in many essential cellular processes has become more evident as the lack of a stable tertiary structure of many protagonists in signal transduction, transcription regulation and cell-cycle regulation has been discovered. The growing demand for structural data of IDPs required the development and adaption of methods such as ¹³C-direct detected experiments, paramagnetic relaxation enhancements (PREs) or residual dipolar couplings (RDCs) for the study of ‘unstructured’ molecules in vitro and in-cell. The information obtained by NMR can be processed with novel computational tools to generate conformational ensembles that visualize the conformations IDPs sample under functional conditions. Here, we address NMR experiments and strategies that enable the generation of detailed structural models of IDPs. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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Ensemble-Based Interpretations of NMR Structural Data to Describe Protein Internal Dynamics

by Annamária F. Ángyán and Zoltán Gáspári

Molecules 2013, 18(9), 10548-10567; https://doi.org/10.3390/molecules180910548 - 30 Aug 2013

Cited by 26 | Viewed by 8406

Abstract

NMR spectroscopy is the leading technique to characterize protein internal dynamics at the atomic level and on multiple time scales. However, the structural interpretation of the observables obtained by various measurements is not always straightforward and in many cases dynamics-related parameters are only [...] Read more.

NMR spectroscopy is the leading technique to characterize protein internal dynamics at the atomic level and on multiple time scales. However, the structural interpretation of the observables obtained by various measurements is not always straightforward and in many cases dynamics-related parameters are only used to “decorate” static structural models without offering explicit description of conformational heterogeneity. To overcome such limitations, several computational techniques have been developed to generate ensemble-based representations of protein structure and dynamics with the use of NMR-derived data. An important common aspect of the methods is that NMR observables and derived parameters are interpreted as properties of the ensemble instead of individual conformers. The resulting ensembles reflect the experimentally determined internal mobility of proteins at a given time scale and can be used to understand the role of internal motions in biological processes at atomic detail. In this review we provide an overview of the calculation methods currently available and examples of biological insights obtained by the ensemble-based models of the proteins investigated. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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Probing Early Misfolding Events in Prion Protein Mutants by NMR Spectroscopy

by Gabriele Giachin, Ivana Biljan, Gregor Ilc, Janez Plavec and Giuseppe Legname

Molecules 2013, 18(8), 9451-9476; https://doi.org/10.3390/molecules18089451 - 7 Aug 2013

Cited by 32 | Viewed by 9737

Abstract

The post-translational conversion of the ubiquitously expressed cellular form of the prion protein, PrP^C, into its misfolded and pathogenic isoform, known as prion or PrP^Sc, plays a key role in prion diseases. These maladies are denoted transmissible spongiform encephalopathies [...] Read more.

The post-translational conversion of the ubiquitously expressed cellular form of the prion protein, PrP^C, into its misfolded and pathogenic isoform, known as prion or PrP^Sc, plays a key role in prion diseases. These maladies are denoted transmissible spongiform encephalopathies (TSEs) and affect both humans and animals. A prerequisite for understanding TSEs is unraveling the molecular mechanism leading to the conversion process whereby most α-helical motifs are replaced by β-sheet secondary structures. Importantly, most point mutations linked to inherited prion diseases are clustered in the C-terminal domain region of PrP^C and cause spontaneous conversion to PrP^Sc. Structural studies with PrP variants promise new clues regarding the proposed conversion mechanism and may help identify “hot spots” in PrP^C involved in the pathogenic conversion. These investigations may also shed light on the early structural rearrangements occurring in some PrP^C epitopes thought to be involved in modulating prion susceptibility. Here we present a detailed overview of our solution-state NMR studies on human prion protein carrying different pathological point mutations and the implications that such findings may have for the future of prion research. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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Contributions of NMR to the Understanding of the Coordination Chemistry and DNA Interactions of Metallo-Bleomycins

by Teresa Lehmann and Elena Topchiy

Molecules 2013, 18(8), 9253-9277; https://doi.org/10.3390/molecules18089253 - 2 Aug 2013

Cited by 6 | Viewed by 6258

Abstract

Bleomycins are a family of glycopeptide antibiotics that have the ability to bind and degrade DNA when bound to key metal ions, which is believed to be responsible for their antitumor activity. Knowledge of the structures of metallo-bleomycins is vital to further characterize [...] Read more.

Bleomycins are a family of glycopeptide antibiotics that have the ability to bind and degrade DNA when bound to key metal ions, which is believed to be responsible for their antitumor activity. Knowledge of the structures of metallo-bleomycins is vital to further characterize their mechanism of action. To this end, numerous structural studies on metallo-bleomycins have been conducted. NMR spectroscopy has had a key role in most of these studies, and has led to very important findings involving the coordination chemistry of metallo-bleomycins, and the details of many metallo-bleomycin-DNA spatial correlations for this important drug. This paper reviews the most important contributions of NMR to the bleomycin field. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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Solution NMR Studies on the Orientation of Membrane-Bound Peptides and Proteins by Paramagnetic Probes

by Evelyne Schrank, Gabriel E. Wagner and Klaus Zangger

Molecules 2013, 18(7), 7407-7435; https://doi.org/10.3390/molecules18077407 - 25 Jun 2013

Cited by 24 | Viewed by 7787

Abstract

Many peptides and proteins are attached to or immersed in a biological membrane. In order to understand their function not only the structure but also their topology in the membrane is important. Solution NMR spectroscopy is one of the most often used approaches [...] Read more.

Many peptides and proteins are attached to or immersed in a biological membrane. In order to understand their function not only the structure but also their topology in the membrane is important. Solution NMR spectroscopy is one of the most often used approaches to determine the orientation and localization of membrane-bound peptides and proteins. Here we give an application-oriented overview on the use of paramagnetic probes for the investigation of membrane-bound peptides and proteins. The examples discussed range from the large pool of antimicrobial peptides, bacterial toxins, cell penetrating peptides to domains of larger proteins or the calcium regulating protein phospholamban. Topological information is obtained in all these examples by the use of either attached or freely mobile paramagnetic tags. For some examples information obtained from the paramagnetic probes was included in the structure determination. Full article

(This article belongs to the Special Issue NMR of Proteins and Small Biomolecules)

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