1
|
Abstract
Proteins have dynamic structures that undergo chain motions on time scales spanning from picoseconds to seconds. Resolving the resultant conformational heterogeneity is essential for gaining accurate insight into fundamental mechanistic aspects of the protein folding reaction. The use of high-resolution structural probes, sensitive to population distributions, has begun to enable the resolution of site-specific conformational heterogeneity at different stages of the folding reaction. Different states populated during protein folding, including the unfolded state, collapsed intermediate states, and even the native state, are found to possess significant conformational heterogeneity. Heterogeneity in protein folding and unfolding reactions originates from the reduced cooperativity of various kinds of physicochemical interactions between various structural elements of a protein, and between a protein and solvent. Heterogeneity may arise because of functional or evolutionary constraints. Conformational substates within the unfolded state and the collapsed intermediates that exchange at rates slower than the subsequent folding steps give rise to heterogeneity on the protein folding pathways. Multiple folding pathways are likely to represent distinct sequences of structure formation. Insight into the nature of the energy barriers separating different conformational states populated during (un)folding can also be obtained by resolving heterogeneity.
Collapse
Affiliation(s)
- Sandhya Bhatia
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India.,Indian Institute of Science Education and Research, Pune 411008, India
| | - Jayant B Udgaonkar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India.,Indian Institute of Science Education and Research, Pune 411008, India
| |
Collapse
|
2
|
Leavens MJ, Spang LE, Cherney MM, Bowler BE. Denatured State Conformational Biases in Three-Helix Bundles Containing Divergent Sequences Localize near Turns and Helix Capping Residues. Biochemistry 2021; 60:3071-3085. [PMID: 34606713 PMCID: PMC8751257 DOI: 10.1021/acs.biochem.1c00400] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rhodopseudomonas palustris cytochrome c', a four-helix bundle, and the second ubiquitin-associated domain, UBA(2), a three-helix bundle from the human homologue of yeast Rad23, HHR23A, deviate from random coil behavior under denaturing conditions in a fold-specific manner. The random coil deviations in each of these folds occur near interhelical turns and loops in their tertiary structures. Here, we examine an additional three-helix bundle with an identical fold to UBA(2), but a highly divergent sequence, the first ubiquitin-associated domain, UBA(1), of HHR23A. We use histidine-heme loop formation methods, employing eight single histidine variants, to probe for denatured state conformational bias of a UBA(1) domain fused to the N-terminus of iso-1-cytochrome c (iso-1-Cytc). Guanidine hydrochloride (GuHCl) denaturation shows that the iso-1-Cytc domain unfolds first, followed by the UBA(1) domain. Denatured state (4 and 6 M GuHCl) histidine-heme loop formation studies show that as the size of the histidine-heme loop increases, loop stability decreases, as expected for the Jacobson-Stockmayer relationship. However, loops formed with His35, His31, and His15, of UBA(1), are 0.6-1.1 kcal/mol more stable than expected from the Jacobson-Stockmayer relationship, confirming the importance of deviations of the denatured state from random coil behavior near interhelical turns of helical domains for facilitating folding to the correct topology. For UBA(1) and UBA(2), hydrophobic clusters on either side of the turns partially explain deviations from random coil behavior; however, helix capping also appears to be important.
Collapse
Affiliation(s)
- Moses J. Leavens
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Lisa E. Spang
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Melisa M. Cherney
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Bruce E. Bowler
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| |
Collapse
|
3
|
From folding to function: complex macromolecular reactions unraveled one-by-one with optical tweezers. Essays Biochem 2021; 65:129-142. [PMID: 33438724 DOI: 10.1042/ebc20200024] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 12/08/2020] [Accepted: 12/11/2020] [Indexed: 12/13/2022]
Abstract
Single-molecule manipulation with optical tweezers has uncovered macromolecular behaviour hidden to other experimental techniques. Recent instrumental improvements have made it possible to expand the range of systems accessible to optical tweezers. Beyond focusing on the folding and structural changes of isolated single molecules, optical tweezers studies have evolved into unraveling the basic principles of complex molecular processes such as co-translational folding on the ribosome, kinase activation dynamics, ligand-receptor binding, chaperone-assisted protein folding, and even dynamics of intrinsically disordered proteins (IDPs). In this mini-review, we illustrate the methodological principles of optical tweezers before highlighting recent advances in studying complex protein conformational dynamics - from protein synthesis to physiological function - as well as emerging future issues that are beginning to be addressed with novel approaches.
Collapse
|
4
|
Sonar P, Bellucci L, Mossa A, Heidarsson PO, Kragelund BB, Cecconi C. Effects of Ligand Binding on the Energy Landscape of Acyl-CoA-Binding Protein. Biophys J 2020; 119:1821-1832. [PMID: 33080224 PMCID: PMC7677128 DOI: 10.1016/j.bpj.2020.09.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 08/14/2020] [Accepted: 09/08/2020] [Indexed: 12/19/2022] Open
Abstract
Binding of ligands is often crucial for function yet the effects of ligand binding on the mechanical stability and energy landscape of proteins are incompletely understood. Here, we use a combination of single-molecule optical tweezers and MD simulations to investigate the effect of ligand binding on the energy landscape of acyl-coenzyme A (CoA)-binding protein (ACBP). ACBP is a topologically simple and highly conserved four-α-helix bundle protein that acts as an intracellular transporter and buffer for fatty-acyl-CoA and is active in membrane assembly. We have previously described the behavior of ACBP under tension, revealing a highly extended transition state (TS) located almost halfway between the unfolded and native states. Here, we performed force-ramp and force-jump experiments, in combination with advanced statistical analysis, to show that octanoyl-CoA binding increases the activation free energy for the unfolding reaction of ACBP without affecting the position of the transition state along the reaction coordinate. It follows that ligand binding enhances the mechanical resistance and thermodynamic stability of the protein, without changing its mechanical compliance. Steered molecular dynamics simulations allowed us to rationalize the results in terms of key interactions that octanoyl-CoA establishes with the four α-helices of ACBP and showed that the unfolding pathway is marginally affected by the ligand. The results show that ligand-induced mechanical stabilization effects can be complex and may prove useful for the rational design of stabilizing ligands.
Collapse
Affiliation(s)
- Punam Sonar
- Physik-Department E22, Technische Universität München, Garching Germany
| | - Luca Bellucci
- NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, Piazza San Silvestro 12, Pisa, Italy
| | - Alessandro Mossa
- INFN Firenze, Sesto Fiorentino, Italy; Istituto Statale di Istruzione Superiore "Leonardo da Vinci", Firenze, Italy.
| | - Pétur O Heidarsson
- Department of Biochemistry, Science Institute, University of Iceland, Reykjavík, Iceland.
| | - Birthe B Kragelund
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Copenhagen N, Denmark.
| | - Ciro Cecconi
- Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, Modena, Italy; Center S3, CNR Institute Nanoscience, Modena, Italy.
| |
Collapse
|
5
|
Charmpilas N, Ruckenstuhl C, Sica V, Büttner S, Habernig L, Dichtinger S, Madeo F, Tavernarakis N, Bravo-San Pedro JM, Kroemer G. Acyl-CoA-binding protein (ACBP): a phylogenetically conserved appetite stimulator. Cell Death Dis 2020; 11:7. [PMID: 31907349 PMCID: PMC6944704 DOI: 10.1038/s41419-019-2205-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 12/12/2019] [Accepted: 12/12/2019] [Indexed: 12/31/2022]
Abstract
Recently, we reported that, in mice, hunger causes the autophagy-dependent release of a protein called "acyl-CoA-binding protein" or "diazepam binding inhibitor" (ACBP/DBI) from cells, resulting in an increase in plasma ACBP concentrations. Administration of extra ACBP is orexigenic and obesogenic, while its neutralization is anorexigenic in mice, suggesting that ACBP is a major stimulator of appetite and lipo-anabolism. Accordingly, obese persons have higher circulating ACBP levels than lean individuals, and anorexia nervosa is associated with subnormal ACBP plasma concentrations. Here, we investigated whether ACBP might play a phylogenetically conserved role in appetite stimulation. We found that extracellular ACBP favors sporulation in Saccharomyces cerevisiae, knowing that sporulation is a strategy for yeast to seek new food sources. Moreover, in the nematode Caenorhabditis elegans, ACBP increased the ingestion of bacteria as well as the frequency pharyngeal pumping. These observations indicate that ACBP has a phylogenetically ancient role as a 'hunger factor' that favors food intake.
Collapse
Affiliation(s)
- Nikolaos Charmpilas
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Nikolaou Plastira 100, 70013, Heraklion, Crete, Greece
- Department of Biology, University of Crete, 70013, Heraklion, Crete, Greece
| | - Christoph Ruckenstuhl
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Humboldtstrasse 50, 8010, Graz, Austria
| | - Valentina Sica
- Metabolomics and Cell Biology Platforms, Gustave Roussy Cancer Campus, Villejuif, France
- Inserm U1138, Centre de Recherche des Cordeliers, Sorbonne Universite, Universite de Paris, 15-rue de l'ecole de medecine, 75006, Paris, France
- Team "Metabolism, Cancer & Immunity", equipe 11 labellisee par la Ligue contre le Cancer, Paris, France
| | - Sabrina Büttner
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Humboldtstrasse 50, 8010, Graz, Austria
- Department of Molecular Biosciences, The Wenner Gren Institute, Stockholm University, Stockholm, Sweden
| | - Lukas Habernig
- Department of Molecular Biosciences, The Wenner Gren Institute, Stockholm University, Stockholm, Sweden
| | - Silvia Dichtinger
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Humboldtstrasse 50, 8010, Graz, Austria
| | - Frank Madeo
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Humboldtstrasse 50, 8010, Graz, Austria.
- BioTechMed Graz, Graz, Austria.
| | - Nektarios Tavernarakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Nikolaou Plastira 100, 70013, Heraklion, Crete, Greece.
- Department of Basic Sciences, Faculty of Medicine, University of Crete, 71110, Heraklion, Crete, Greece.
| | - José M Bravo-San Pedro
- Metabolomics and Cell Biology Platforms, Gustave Roussy Cancer Campus, Villejuif, France
- Inserm U1138, Centre de Recherche des Cordeliers, Sorbonne Universite, Universite de Paris, 15-rue de l'ecole de medecine, 75006, Paris, France
- Team "Metabolism, Cancer & Immunity", equipe 11 labellisee par la Ligue contre le Cancer, Paris, France
| | - Guido Kroemer
- Metabolomics and Cell Biology Platforms, Gustave Roussy Cancer Campus, Villejuif, France.
- Inserm U1138, Centre de Recherche des Cordeliers, Sorbonne Universite, Universite de Paris, 15-rue de l'ecole de medecine, 75006, Paris, France.
- Team "Metabolism, Cancer & Immunity", equipe 11 labellisee par la Ligue contre le Cancer, Paris, France.
- Pole de Biologie, Hopital Europeen Georges Pompidou, AP-HP, Paris, France.
- Suzhou Institute for Systems Medicine, Chinese Academy of Sciences, Suzhou, China.
- Karolinska Institute, Department of Women's and Children's Health, Karolinska University Hospital, Stockholm, Sweden.
| |
Collapse
|
6
|
Obtaining Hydrodynamic Radii of Intrinsically Disordered Protein Ensembles by Pulsed Field Gradient NMR Measurements. Methods Mol Biol 2020; 2141:285-302. [PMID: 32696363 DOI: 10.1007/978-1-0716-0524-0_14] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
In the disordered state, a protein exhibits a high degree of structural freedom, in both space and time. For an ensemble of disordered or unfolded proteins, this means that the ensemble comprises a high diversity of structures, ranging from compact collapsed states to fully extended polypeptide chains. In addition, each chain is highly dynamic and undergoes conformational changes and local dynamics on both fast and slow timescales. The size properties of disordered proteins are thus best described as ensemble averages. A straightforward measure of the size is the hydrodynamic radius, RH, of the ensemble. Since the disordered state is conformationally fluid, the observed RH does not refer to a particular shape or fold. Instead, it should be interpreted as a measure for the average compaction of the structural ensemble. In addition to characterizing the disordered ensemble itself, RH can be used to, with good precision, monitor changes in the ensemble size properties upon functional interactions of the disordered protein, e.g., dimerization, ligand binding, and folding pathways. Here, we present a step-by-step protocol for diffusion measurements using pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy. We describe how to calibrate the magnetic field gradient and offer different schemes for sample preparation. Finally, we describe how to obtain RH directly from the diffusion coefficient as well as from using an internal standard as a reference.
Collapse
|
7
|
Munshi S, Subramanian S, Ramesh S, Golla H, Kalivarathan D, Kulkarni M, Campos LA, Sekhar A, Naganathan AN. Engineering Order and Cooperativity in a Disordered Protein. Biochemistry 2019; 58:2389-2397. [PMID: 31002232 DOI: 10.1021/acs.biochem.9b00182] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Structural disorder in proteins arises from a complex interplay between weak hydrophobicity and unfavorable electrostatic interactions. The extent to which the hydrophobic effect contributes to the unique and compact native state of proteins is, however, confounded by large compensation between multiple entropic and energetic terms. Here we show that protein structural order and cooperativity arise as emergent properties upon hydrophobic substitutions in a disordered system with non-intuitive effects on folding and function. Aided by sequence-structure analysis, equilibrium, and kinetic spectroscopic studies, we engineer two hydrophobic mutations in the disordered DNA-binding domain of CytR that act synergistically, but not in isolation, to promote structure, compactness, and stability. The double mutant, with properties of a fully ordered domain, exhibits weak cooperativity with a complex and rugged conformational landscape. The mutant, however, binds cognate DNA with an affinity only marginally higher than that of the wild type, though nontrivial differences are observed in the binding to noncognate DNA. Our work provides direct experimental evidence of the dominant role of non-additive hydrophobic effects in shaping the molecular evolution of order in disordered proteins and vice versa, which could be generalized to even folded proteins with implications for protein design and functional manipulation.
Collapse
Affiliation(s)
- Sneha Munshi
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| | - Sandhyaa Subramanian
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| | - Samyuktha Ramesh
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| | - Hemashree Golla
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| | - Divakar Kalivarathan
- Department of Biotechnology , National Institute of Technology Warangal , Warangal 506004 , India
| | - Madhurima Kulkarni
- Molecular Biophysics Unit , Indian Institute of Science , Bangalore 560012 , India
| | - Luis A Campos
- National Biotechnology Center , Consejo Superior de Investigaciones Científicas , Darwin 3, Campus de Cantoblanco , 28049 Madrid , Spain
| | - Ashok Sekhar
- Molecular Biophysics Unit , Indian Institute of Science , Bangalore 560012 , India
| | - Athi N Naganathan
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| |
Collapse
|
8
|
Abstract
In this review, I discuss the various methods researchers use to unfold proteins in the lab in order to understand protein folding both
in vitro and
in vivo. The four main techniques, chemical-, heat-, pressure- and force-denaturation, produce distinctly different unfolded conformational ensembles. Recent measurements have revealed different folding kinetics from different unfolding mechanisms. Thus, comparing these distinct unfolded ensembles sheds light on the underlying free energy landscape of folding.
Collapse
Affiliation(s)
- Lisa J Lapidus
- Department of Physics and Astronomy, Michigan State University, East Lansing, USA
| |
Collapse
|
9
|
Ota C, Ikeguchi M, Tanaka A, Hamada D. Residual structures in the unfolded state of starch-binding domain of glucoamylase revealed by near-UV circular dichroism and protein engineering techniques. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1464-72. [PMID: 27164491 DOI: 10.1016/j.bbapap.2016.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/03/2016] [Accepted: 05/05/2016] [Indexed: 11/29/2022]
Abstract
Protein folding is a thermodynamic process driven by energy gaps between the native and unfolded states. Although a wealth of information is available on the structure of folded species, there is a paucity of data on unfolded species. Here, we analyzed the structural properties of the unfolded state of the starch-binding domain of glucoamylase from Aspergillus niger (SBD) formed in the presence of guanidinium hydrochloride (GuHCl). Although far-UV CD and intrinsic tryptophan fluorescence spectra as well as small angle X-ray scattering suggested that SBD assumes highly unfolded structures in the presence of GuHCl, near-UV circular dichroism of wild-type SBD suggested the presence of residual structures in the unfolded state. Analyses of the unfolded states of tryptophan mutants (W543L, W563A, W590A and W615L) using Similarity Parameter, a modified version of root mean square deviation as a measure of similarity between two spectra, suggested that W543 and W563 have preferences to form native-like residual structures in the GuHCl-unfolded state. In contrast, W615 was entirely unstructured, while W590 tended to form non-native ordered structures in the unfolded state. These data and the amino acid sequence of SBD suggest that local structural propensities in the unfolded state can be determined by the probability of the presence of hydrophobic or charged residues nearby tryptophan residues.
Collapse
Affiliation(s)
- Chiaki Ota
- Department of Life Science, Faculty of Bioresources, Mie University, 1577 Kurimamachiya, Tsu, Mie 514-8507, Japan
| | - Masamichi Ikeguchi
- Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan
| | - Akiyoshi Tanaka
- Department of Life Science, Faculty of Bioresources, Mie University, 1577 Kurimamachiya, Tsu, Mie 514-8507, Japan
| | - Daizo Hamada
- Department of Life Science, Faculty of Bioresources, Mie University, 1577 Kurimamachiya, Tsu, Mie 514-8507, Japan; Graduate School of Engineering and Center for Applied Structural Science (CASS), Kobe University, 7-1-48 Minatojima Minami Machi, Chuo-ku, Kobe 650-0047, Japan.
| |
Collapse
|
10
|
Munshi S, Naganathan AN. Imprints of function on the folding landscape: functional role for an intermediate in a conserved eukaryotic binding protein. Phys Chem Chem Phys 2016; 17:11042-52. [PMID: 25824585 DOI: 10.1039/c4cp06102k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In the computational characterization of single domain protein folding, the effective free energies of numerous microstates are projected onto few collective degrees of freedom that in turn serve as well-defined reaction coordinates. In this regard, one-dimensional (1D) free energy profiles are widely used mainly for their simplicity. Since folding and functional landscapes are interlinked, how well can these reduced representations capture the structural and dynamic features of functional states while being simultaneously consistent with experimental observables? We investigate this issue by characterizing the folding of the four-helix bundle bovine acyl-CoA binding protein (bACBP), which exhibits complex equilibrium and kinetic behaviours, employing an Ising-like statistical mechanical model and molecular simulations. We show that the features of the 1D free energy profile are sufficient to quantitatively reproduce multiple experimental observations including millisecond chevron-like kinetics and temperature dependence, a microsecond fast phase, barrier heights, unfolded state movements, the intermediate structure and average ϕ-values. Importantly, we find that the structural features of the native-like intermediate (partial disorder in helix 1) are intricately linked to a unique interplay between packing and electrostatics in this domain. By comparison with available experimental data, we propose that this intermediate determines the promiscuous functional behaviour of bACBP that exhibits broad substrate specificity. Our results present evidence to the possibility of employing the statistical mechanical model and the resulting 1D free energy profile to not just understand folding mechanisms but to even extract features of functionally relevant states and their energetic origins.
Collapse
Affiliation(s)
- Sneha Munshi
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India.
| | | |
Collapse
|
11
|
Roche J, Shen Y, Lee JH, Ying J, Bax A. Monomeric Aβ(1-40) and Aβ(1-42) Peptides in Solution Adopt Very Similar Ramachandran Map Distributions That Closely Resemble Random Coil. Biochemistry 2016; 55:762-75. [PMID: 26780756 PMCID: PMC4750080 DOI: 10.1021/acs.biochem.5b01259] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
![]()
The
pathogenesis of Alzheimer’s disease is characterized
by the aggregation and fibrillation of amyloid peptides Aβ1–40 and Aβ1–42 into amyloid
plaques. Despite strong potential therapeutic interest, the structural
pathways associated with the conversion of monomeric Aβ peptides
into oligomeric species remain largely unknown. In particular, the
higher aggregation propensity and associated toxicity of Aβ1–42 compared to that of Aβ1–40 are poorly understood. To explore in detail the structural propensity
of the monomeric Aβ1–40 and Aβ1–42 peptides in solution, we recorded a large set of nuclear magnetic
resonance (NMR) parameters, including chemical shifts, nuclear Overhauser
effects (NOEs), and J couplings. Systematic comparisons
show that at neutral pH the Aβ1–40 and Aβ1–42 peptides populate almost indistinguishable coil-like
conformations. Nuclear Overhauser effect spectra collected at very
high resolution remove assignment ambiguities and show no long-range
NOE contacts. Six sets of backbone J couplings (3JHNHα, 3JC′C′, 3JC′Hα, 1JHαCα, 2JNCα, and 1JNCα) recorded
for Aβ1–40 were used as input for the recently
developed MERA Ramachandran map analysis, yielding residue-specific
backbone ϕ/ψ torsion angle distributions that closely
resemble random coil distributions, the absence of a significantly
elevated propensity for β-conformations in the C-terminal region
of the peptide, and a small but distinct propensity for αL at K28. Our results suggest that the self-association of
Aβ peptides into toxic oligomers is not driven by elevated propensities
of the monomeric species to adopt β-strand-like conformations.
Instead, the accelerated disappearance of Aβ NMR signals in
D2O over H2O, particularly pronounced for Aβ1–42, suggests that intermolecular interactions between
the hydrophobic regions of the peptide dominate the aggregation process.
Collapse
Affiliation(s)
- Julien Roche
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0510, United States
| | - Yang Shen
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0510, United States
| | - Jung Ho Lee
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0510, United States
| | - Jinfa Ying
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0510, United States
| | - Ad Bax
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0510, United States
| |
Collapse
|
12
|
Where the complex things are: single molecule and ensemble spectroscopic investigations of protein folding dynamics. Curr Opin Struct Biol 2015; 36:1-9. [PMID: 26687767 DOI: 10.1016/j.sbi.2015.11.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 11/10/2015] [Indexed: 01/11/2023]
Abstract
Progress in our understanding of the simple folding dynamics of small proteins and the complex dynamics of large proteins is reviewed. Recent characterizations of the folding transition path of small proteins revealed a simple dynamics explainable by the native centric model. In contrast, the accumulated data showed the substates containing residual structures in the unfolded state and partially populated intermediates, causing complexity in the early folding dynamics of small proteins. The size of the unfolded proteins in the absence of denaturants is likely expanded but still controversial. The steady progress in the observation of folding of large proteins has clarified the rapid formation of long-range contacts that seem inconsistent with the native centric model, suggesting that the folding strategy of large proteins is distinct from that of small proteins.
Collapse
|
13
|
Pastor N, Amero C. Information flow and protein dynamics: the interplay between nuclear magnetic resonance spectroscopy and molecular dynamics simulations. FRONTIERS IN PLANT SCIENCE 2015; 6:306. [PMID: 25999971 PMCID: PMC4419604 DOI: 10.3389/fpls.2015.00306] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 04/17/2015] [Indexed: 06/04/2023]
Abstract
Proteins participate in information pathways in cells, both as links in the chain of signals, and as the ultimate effectors. Upon ligand binding, proteins undergo conformation and motion changes, which can be sensed by the following link in the chain of information. Nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations represent powerful tools for examining the time-dependent function of biological molecules. The recent advances in NMR and the availability of faster computers have opened the door to more detailed analyses of structure, dynamics, and interactions. Here we briefly describe the recent applications that allow NMR spectroscopy and MD simulations to offer unique insight into the basic motions that underlie information transfer within and between cells.
Collapse
Affiliation(s)
- Nina Pastor
- Laboratorio de Dinámica de Proteínas y Ácidos Nucleicos, Centro de Investigación en Dinámica Celular, Universidad Autónoma del Estado de Morelos, Cuernavaca, Mexico
| | - Carlos Amero
- Laboratorio de Bioquímica y Resonancia Magnética Nuclear, Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Cuernavaca, Mexico
| |
Collapse
|
14
|
Abstract
Myriad biological processes proceed through states that defy characterization by conventional atomic-resolution structural biological methods. The invisibility of these 'dark' states can arise from their transient nature, low equilibrium population, large molecular weight, and/or heterogeneity. Although they are invisible, these dark states underlie a range of processes, acting as encounter complexes between proteins and as intermediates in protein folding and aggregation. New methods have made these states accessible to high-resolution analysis by nuclear magnetic resonance (NMR) spectroscopy, as long as the dark state is in dynamic equilibrium with an NMR-visible species. These methods - paramagnetic NMR, relaxation dispersion, saturation transfer, lifetime line broadening, and hydrogen exchange - allow the exploration of otherwise invisible states in exchange with a visible species over a range of timescales, each taking advantage of some unique property of the dark state to amplify its effect on a particular NMR observable. In this review, we introduce these methods and explore two specific techniques - paramagnetic relaxation enhancement and dark state exchange saturation transfer - in greater detail.
Collapse
Affiliation(s)
- Nicholas J. Anthis
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, USA
| | - G. Marius Clore
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, USA
| |
Collapse
|
15
|
McMorran LM, Brockwell DJ, Radford SE. Mechanistic studies of the biogenesis and folding of outer membrane proteins in vitro and in vivo: what have we learned to date? Arch Biochem Biophys 2014; 564:265-80. [PMID: 24613287 PMCID: PMC4262575 DOI: 10.1016/j.abb.2014.02.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 02/16/2014] [Accepted: 02/20/2014] [Indexed: 11/17/2022]
Abstract
Research into the mechanisms by which proteins fold into their native structures has been on-going since the work of Anfinsen in the 1960s. Since that time, the folding mechanisms of small, water-soluble proteins have been well characterised. By contrast, progress in understanding the biogenesis and folding mechanisms of integral membrane proteins has lagged significantly because of the need to create a membrane mimetic environment for folding studies in vitro and the difficulties in finding suitable conditions in which reversible folding can be achieved. Improved knowledge of the factors that promote membrane protein folding and disfavour aggregation now allows studies of folding into lipid bilayers in vitro to be performed. Consequently, mechanistic details and structural information about membrane protein folding are now emerging at an ever increasing pace. Using the panoply of methods developed for studies of the folding of water-soluble proteins. This review summarises current knowledge of the mechanisms of outer membrane protein biogenesis and folding into lipid bilayers in vivo and in vitro and discusses the experimental techniques utilised to gain this information. The emerging knowledge is beginning to allow comparisons to be made between the folding of membrane proteins with current understanding of the mechanisms of folding of water-soluble proteins.
Collapse
Affiliation(s)
- Lindsay M McMorran
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK.
| |
Collapse
|
16
|
Camilloni C, Vendruscolo M. Statistical mechanics of the denatured state of a protein using replica-averaged metadynamics. J Am Chem Soc 2014; 136:8982-91. [PMID: 24884637 DOI: 10.1021/ja5027584] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The characterization of denatured states of proteins is challenging because the lack of permanent structure in these states makes it difficult to apply to them standard methods of structural biology. In this work we use all-atom replica-averaged metadynamics (RAM) simulations with NMR chemical shift restraints to determine an ensemble of structures representing an acid-denatured state of the 86-residue protein ACBP. This approach has enabled us to reach convergence in the free energy landscape calculations, obtaining an ensemble of structures in relatively accurate agreement with independent experimental data used for validation. By observing at atomistic resolution the transient formation of native and non-native structures in this acid-denatured state of ACBP, we rationalize the effects of single-point mutations on the folding rate, stability, and transition-state structures of this protein, thus characterizing the role of the unfolded state in determining the folding process.
Collapse
Affiliation(s)
- Carlo Camilloni
- Department of Chemistry, University of Cambridge , Cambridge CB2 1EW, United Kingdom
| | | |
Collapse
|
17
|
Jensen MR, Zweckstetter M, Huang JR, Blackledge M. Exploring free-energy landscapes of intrinsically disordered proteins at atomic resolution using NMR spectroscopy. Chem Rev 2014; 114:6632-60. [PMID: 24725176 DOI: 10.1021/cr400688u] [Citation(s) in RCA: 214] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|