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Sun H, Guo Z, Hong H, Zhang Z, Zhang Y, Wang Y, Le S, Chen H. Free Energy Landscape of Type III Fibronectin Domain with Identified Intermediate State and Hierarchical Symmetry. PHYSICAL REVIEW LETTERS 2023; 131:218402. [PMID: 38072617 DOI: 10.1103/physrevlett.131.218402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Accepted: 10/23/2023] [Indexed: 12/18/2023]
Abstract
The tenth domain of type III fibronectin (FNIII_{10}) mediates cell adhesion to the extracellular matrix. Despite its structural similarity to immunoglobulin domains, FNIII_{10} exhibits unique unfolding behaviors. We employed magnetic tweezers to investigate the unfolding and folding dynamics of FNIII_{10} under physiological forces (4-50 pN). Our results showed that FNIII_{10} follows a consistent transition pathway with an intermediate state characterized by detached A and G β strands. We determined the folding free energies and all force-dependent transition rates of FNIII_{10} and found that both unfolding rates from the native state to the intermediate state and from the intermediate state to the unfolded state deviate from Bell's model. We constructed a quantitative free energy landscape with well-defined traps and barriers that exhibits a hierarchical symmetrical pattern. Our findings provide a comprehensive understanding of FNIII_{10} conformational dynamics and demonstrate how free energy landscape of multistate biomolecules can be precisely mapped, illuminating the relationship between thermal stability, intermediate states, and folding rates in protein folding.
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Affiliation(s)
- Hao Sun
- Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Lab for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen 361005, China
- Center of Biomedical Physics, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, China
| | - Zilong Guo
- Center of Biomedical Physics, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, China
| | - Haiyan Hong
- Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Lab for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen 361005, China
| | - Zhuwei Zhang
- Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Lab for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen 361005, China
- Center of Biomedical Physics, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, China
| | - Yuhang Zhang
- Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Lab for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen 361005, China
| | - Yang Wang
- Center of Biomedical Physics, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, China
| | - Shimin Le
- Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Lab for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen 361005, China
| | - Hu Chen
- Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Lab for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen 361005, China
- Center of Biomedical Physics, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, China
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Mitra R, Gadkari VV, Meinen BA, van Mierlo CPM, Ruotolo BT, Bardwell JCA. Mechanism of the small ATP-independent chaperone Spy is substrate specific. Nat Commun 2021; 12:851. [PMID: 33558474 PMCID: PMC7870927 DOI: 10.1038/s41467-021-21120-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 01/08/2021] [Indexed: 11/17/2022] Open
Abstract
ATP-independent chaperones are usually considered to be holdases that rapidly bind to non-native states of substrate proteins and prevent their aggregation. These chaperones are thought to release their substrate proteins prior to their folding. Spy is an ATP-independent chaperone that acts as an aggregation inhibiting holdase but does so by allowing its substrate proteins to fold while they remain continuously chaperone bound, thus acting as a foldase as well. The attributes that allow such dual chaperoning behavior are unclear. Here, we used the topologically complex protein apoflavodoxin to show that the outcome of Spy's action is substrate specific and depends on its relative affinity for different folding states. Tighter binding of Spy to partially unfolded states of apoflavodoxin limits the possibility of folding while bound, converting Spy to a holdase chaperone. Our results highlight the central role of the substrate in determining the mechanism of chaperone action.
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Affiliation(s)
- Rishav Mitra
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Varun V Gadkari
- Department of Chemistry, University of Michigan, Ann Arbor, MI, USA
| | - Ben A Meinen
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | | | | | - James C A Bardwell
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI, USA.
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
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3
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Banach M, Prudhomme N, Carpentier M, Duprat E, Papandreou N, Kalinowska B, Chomilier J, Roterman I. Contribution to the prediction of the fold code: application to immunoglobulin and flavodoxin cases. PLoS One 2015; 10:e0125098. [PMID: 25915049 PMCID: PMC4411048 DOI: 10.1371/journal.pone.0125098] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 03/20/2015] [Indexed: 12/19/2022] Open
Abstract
Background Folding nucleus of globular proteins formation starts by the mutual interaction of a group of hydrophobic amino acids whose close contacts allow subsequent formation and stability of the 3D structure. These early steps can be predicted by simulation of the folding process through a Monte Carlo (MC) coarse grain model in a discrete space. We previously defined MIRs (Most Interacting Residues), as the set of residues presenting a large number of non-covalent neighbour interactions during such simulation. MIRs are good candidates to define the minimal number of residues giving rise to a given fold instead of another one, although their proportion is rather high, typically [15-20]% of the sequences. Having in mind experiments with two sequences of very high levels of sequence identity (up to 90%) but different folds, we combined the MIR method, which takes sequence as single input, with the “fuzzy oil drop” (FOD) model that requires a 3D structure, in order to estimate the residues coding for the fold. FOD assumes that a globular protein follows an idealised 3D Gaussian distribution of hydrophobicity density, with the maximum in the centre and minima at the surface of the “drop”. If the actual local density of hydrophobicity around a given amino acid is as high as the ideal one, then this amino acid is assigned to the core of the globular protein, and it is assumed to follow the FOD model. Therefore one obtains a distribution of the amino acids of a protein according to their agreement or rejection with the FOD model. Results We compared and combined MIR and FOD methods to define the minimal nucleus, or keystone, of two populated folds: immunoglobulin-like (Ig) and flavodoxins (Flav). The combination of these two approaches defines some positions both predicted as a MIR and assigned as accordant with the FOD model. It is shown here that for these two folds, the intersection of the predicted sets of residues significantly differs from random selection. It reduces the number of selected residues by each individual method and allows a reasonable agreement with experimentally determined key residues coding for the particular fold. In addition, the intersection of the two methods significantly increases the specificity of the prediction, providing a robust set of residues that constitute the folding nucleus.
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Affiliation(s)
- Mateusz Banach
- Department of Bioinformatics and Telemedicine, Medical College, Jagiellonian University, Krakow, Poland
| | - Nicolas Prudhomme
- Protein Structure Prediction group, IMPMC, UPMC & CNRS, Paris, France
| | - Mathilde Carpentier
- Protein Structure Prediction group, IMPMC, UPMC & CNRS, Paris, France
- RPBS, 35 rue Hélène Brion, 75013, Paris, France
| | - Elodie Duprat
- Protein Structure Prediction group, IMPMC, UPMC & CNRS, Paris, France
- RPBS, 35 rue Hélène Brion, 75013, Paris, France
| | - Nikolaos Papandreou
- Genetics Department, Agricultural University of Athens, Iera Odos 75, Athens, Greece
| | - Barbara Kalinowska
- Department of Bioinformatics and Telemedicine, Medical College, Jagiellonian University, Krakow, Poland
| | - Jacques Chomilier
- Protein Structure Prediction group, IMPMC, UPMC & CNRS, Paris, France
- RPBS, 35 rue Hélène Brion, 75013, Paris, France
- * E-mail: (JC); (IR)
| | - Irena Roterman
- Department of Bioinformatics and Telemedicine, Medical College, Jagiellonian University, Krakow, Poland
- * E-mail: (JC); (IR)
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4
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Evolutionary relationship of two ancient protein superfolds. Nat Chem Biol 2014; 10:710-5. [PMID: 25038785 DOI: 10.1038/nchembio.1579] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 06/02/2014] [Indexed: 01/29/2023]
Abstract
Proteins are the molecular machines of the cell that fold into specific three-dimensional structures to fulfill their functions. To improve our understanding of how the structure and function of proteins arises, it is crucial to understand how evolution has generated the structural diversity we observe today. Classically, proteins that adopt different folds are considered to be nonhomologous. However, using state-of-the-art tools for homology detection, we found evidence of homology between proteins of two ancient and highly populated protein folds, the (βα)8-barrel and the flavodoxin-like fold. We detected a family of sequences that show intermediate features between both folds and determined what is to our knowledge the first representative crystal structure of one of its members, giving new insights into the evolutionary link of two of the earliest folds. Our findings contribute to an emergent vision where protein superfolds share common ancestry and encourage further approaches to complete the mapping of structure space onto sequence space.
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5
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Banach M, Konieczny L, Roterman I. The fuzzy oil drop model, based on hydrophobicity density distribution, generalizes the influence of water environment on protein structure and function. J Theor Biol 2014; 359:6-17. [PMID: 24859428 DOI: 10.1016/j.jtbi.2014.05.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 04/25/2014] [Accepted: 05/05/2014] [Indexed: 12/24/2022]
Abstract
In this paper we show that the fuzzy oil drop model represents a general framework for describing the generation of hydrophobic cores in proteins and thus provides insight into the influence of the water environment upon protein structure and stability. The model has been successfully applied in the study of a wide range of proteins, however this paper focuses specifically on domains representing immunoglobulin-like folds. Here we provide evidence that immunoglobulin-like domains, despite being structurally similar, differ with respect to their participation in the generation of hydrophobic core. It is shown that β-structural fragments in β-barrels participate in hydrophobic core formation in a highly differentiated manner. Quantitatively measured participation in core formation helps explain the variable stability of proteins and is shown to be related to their biological properties. This also includes the known tendency of immunoglobulin domains to form amyloids, as shown using transthyretin to reveal the clear relation between amyloidogenic properties and structural characteristics based on the fuzzy oil drop model.
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Affiliation(s)
- Mateusz Banach
- Department of Bioinformatics and Telemedicine - Jagiellonian University - Medical College, Krakow, Poland; Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, Krakow, Poland
| | - Leszek Konieczny
- Chair of Medical Chemistry - Jagiellonian University - Medical College, Krakow, Poland
| | - Irena Roterman
- Department of Bioinformatics and Telemedicine - Jagiellonian University - Medical College, Krakow, Poland.
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6
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Morris ER, Searle MS. Overview of protein folding mechanisms: experimental and theoretical approaches to probing energy landscapes. CURRENT PROTOCOLS IN PROTEIN SCIENCE 2012; Chapter 28:28.2.1-28.2.22. [PMID: 22470128 DOI: 10.1002/0471140864.ps2802s68] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We present an overview of the current experimental and theoretical approaches to studying protein folding mechanisms, set against current models of the folding energy landscape. We describe how stability and folding kinetics can be determined experimentally and how this data can be interpreted in terms of the characteristic features of various models from the simplest two-state pathway to a multi-state mechanism. We summarize the pros and cons of a range of spectroscopic methods for measuring folding rates and present a theoretical framework, coupled with protein engineering approaches, for elucidating folding mechanisms and structural features of folding transition states. A series of case studies are used to show how experimental kinetic data can be interpreted in the context of non-native interactions, populated intermediates, parallel folding pathways, and sequential transition states. We also show how computational methods now allow transient species of high energy, such as folding transition states, to be modeled on the basis of experimental Φ-value analysis derived from the effects of point mutations on folding kinetics.
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Affiliation(s)
- Elizabeth R Morris
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, Nottingham, United Kingdom
| | - Mark S Searle
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, Nottingham, United Kingdom
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7
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Hills RD, Kathuria SV, Wallace LA, Day IJ, Brooks CL, Matthews CR. Topological frustration in beta alpha-repeat proteins: sequence diversity modulates the conserved folding mechanisms of alpha/beta/alpha sandwich proteins. J Mol Biol 2010; 398:332-50. [PMID: 20226790 DOI: 10.1016/j.jmb.2010.03.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 02/27/2010] [Accepted: 03/03/2010] [Indexed: 10/19/2022]
Abstract
The thermodynamic hypothesis of Anfinsen postulates that structures and stabilities of globular proteins are determined by their amino acid sequences. Chain topology, however, is known to influence the folding reaction, in that motifs with a preponderance of local interactions typically fold more rapidly than those with a larger fraction of nonlocal interactions. Together, the topology and sequence can modulate the energy landscape and influence the rate at which the protein folds to the native conformation. To explore the relationship of sequence and topology in the folding of beta alpha-repeat proteins, which are dominated by local interactions, we performed a combined experimental and simulation analysis on two members of the flavodoxin-like, alpha/beta/alpha sandwich fold. Spo0F and the N-terminal receiver domain of NtrC (NT-NtrC) have similar topologies but low sequence identity, enabling a test of the effects of sequence on folding. Experimental results demonstrated that both response-regulator proteins fold via parallel channels through highly structured submillisecond intermediates before accessing their cis prolyl peptide bond-containing native conformations. Global analysis of the experimental results preferentially places these intermediates off the productive folding pathway. Sequence-sensitive Gō-model simulations conclude that frustration in the folding in Spo0F, corresponding to the appearance of the off-pathway intermediate, reflects competition for intra-subdomain van der Waals contacts between its N- and C-terminal subdomains. The extent of transient, premature structure appears to correlate with the number of isoleucine, leucine, and valine (ILV) side chains that form a large sequence-local cluster involving the central beta-sheet and helices alpha2, alpha 3, and alpha 4. The failure to detect the off-pathway species in the simulations of NT-NtrC may reflect the reduced number of ILV side chains in its corresponding hydrophobic cluster. The location of the hydrophobic clusters in the structure may also be related to the differing functional properties of these response regulators. Comparison with the results of previous experimental and simulation analyses on the homologous CheY argues that prematurely folded unproductive intermediates are a common property of the beta alpha-repeat motif.
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Affiliation(s)
- Ronald D Hills
- Department of Molecular Biology and Kellogg School of Science and Technology, The Scripps Research Institute, 10550 North Torrey Pines Road TPC6, La Jolla, CA 92037, USA
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8
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Different Folding Pathways Taken by Highly Homologous Proteins, Goat α-Lactalbumin and Canine Milk Lysozyme. J Mol Biol 2010; 396:1361-78. [DOI: 10.1016/j.jmb.2010.01.021] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 01/10/2010] [Accepted: 01/11/2010] [Indexed: 11/19/2022]
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9
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Homouz D, Stagg L, Wittung-Stafshede P, Cheung MS. Macromolecular crowding modulates folding mechanism of alpha/beta protein apoflavodoxin. Biophys J 2009; 96:671-80. [PMID: 19167312 DOI: 10.1016/j.bpj.2008.10.014] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Accepted: 10/09/2008] [Indexed: 10/21/2022] Open
Abstract
Protein dynamics in cells may be different from those in dilute solutions in vitro, because the environment in cells is highly concentrated with other macromolecules. This volume exclusion because of macromolecular crowding is predicted to affect both equilibrium and kinetic processes involving protein conformational changes. To quantify macromolecular crowding effects on protein folding mechanisms, we investigated the folding energy landscape of an alpha/beta protein, apoflavodoxin, in the presence of inert macromolecular crowding agents, using in silico and in vitro approaches. By means of coarse-grained molecular simulations and topology-based potential interactions, we probed the effects of increased volume fractions of crowding agents (phi(c)) as well as of crowding agent geometry (sphere or spherocylinder) at high phi(c). Parallel kinetic folding experiments with purified Desulfovibro desulfuricans apoflavodoxin in vitro were performed in the presence of Ficoll (sphere) and Dextran (spherocylinder) synthetic crowding agents. In conclusion, we identified the in silico crowding conditions that best enhance protein stability, and discovered that upon manipulation of the crowding conditions, folding routes experiencing topological frustrations can be either enhanced or relieved. Our test-tube experiments confirmed that apoflavodoxin's time-resolved folding path is modulated by crowding agent geometry. Macromolecular crowding effects may be a tool for the manipulation of protein-folding and function in living cells.
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Affiliation(s)
- Dirar Homouz
- Department of Physics, University of Houston, Houston, Texas, USA
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10
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Reich L, Becker M, Seckler R, Weikl TR. Invivo folding efficiencies for mutants of the P22 tailspike beta-helix protein correlate with predicted stability changes. Biophys Chem 2009; 141:186-92. [PMID: 19254821 DOI: 10.1016/j.bpc.2009.01.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2008] [Revised: 01/29/2009] [Accepted: 01/29/2009] [Indexed: 01/04/2023]
Abstract
Parallel beta-helices are among the simplest repetitive structural elements in proteins. The folding behavior of beta-helix proteins has been studied intensively, also to gain insight on the formation of amyloid fibrils, which share the parallel beta-helix as a central structural motif. An important system for investigating beta-helix folding is the tailspike protein from the Salmonella bacteriophage P22. The central domain of this protein is a right-handed parallel beta-helix with 13 windings. Extensive mutational analyses of the P22 tailspike protein have revealed two main phenotypes: temperature-sensitive-folding (tsf) mutations that reduce the folding efficiency at elevated temperatures, and global suppressor (su) mutations that increase the tailspike folding efficiency. A central question is whether these phenotypes can be understood from changes in the protein stability induced by the mutations. Experimental determination of the protein stability is complicated by the nearly irreversible trimerization of the folded tailspike protein. Here, we present calculations of stability changes with the program FoldX, focusing on a recently published extensive data set of 145 singe-residue alanine mutants. We find that the calculated stability changes are correlated with the experimentally measured invivo folding efficiencies. In addition, we determine the free-energy landscape of the P22 tailspike protein in a nucleation-propagation model to explore the folding mechanism of this protein, and obtain a processive folding route on which the protein nucleates in the N-terminal region of the helix.
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Affiliation(s)
- Lothar Reich
- Max Planck Institute of Colloids and Interfaces, Department of Theory and Bio-Systems, Science Park Golm, 14424 Potsdam, Germany
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11
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Hills RD, Brooks CL. Subdomain competition, cooperativity, and topological frustration in the folding of CheY. J Mol Biol 2008; 382:485-95. [PMID: 18644380 DOI: 10.1016/j.jmb.2008.07.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2008] [Revised: 06/30/2008] [Accepted: 07/04/2008] [Indexed: 11/17/2022]
Abstract
The folding of multidomain proteins often proceeds in a hierarchical fashion with individual domains folding independent of one another. A large single-domain protein, however, can consist of multiple modules whose folding may be autonomous or interdependent in ways that are unclear. We used coarse-grained simulations to explore the folding landscape of the two-subdomain bacterial response regulator CheY. Thermodynamic and kinetic characterization shows the landscape to be highly analogous to the four-state landscape reported for another two-subdomain protein, T4 lysozyme. An on-pathway intermediate structured in the more stable nucleating subdomain was observed, as were transient states frustrated in off-pathway contacts prematurely structured in the weaker subdomain. Local unfolding, or backtracking, was observed in the frustrated state before the native conformation could be reached. Nonproductive frustration was attributable to competition for van der Waals contacts between the two subdomains. In an accompanying article, stopped-flow kinetic measurements support an off-pathway burst-phase intermediate, seemingly consistent with our prediction of early frustration in the folding landscape of CheY. Comparison of the folding mechanisms for CheY, T4 lysozyme, and interleukin-1 beta leads us to postulate that subdomain competition is a general feature of large single-domain proteins with multiple folding modules.
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Affiliation(s)
- Ronald D Hills
- Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, TPC6, La Jolla, CA 92037, USA
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12
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Role of cations in stability of acidic protein Desulfovibrio desulfuricans apoflavodoxin. Arch Biochem Biophys 2008; 474:128-35. [DOI: 10.1016/j.abb.2008.02.037] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Revised: 02/22/2008] [Accepted: 02/25/2008] [Indexed: 11/20/2022]
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13
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Nelson ED, Grishin NV. Folding domain B of protein A on a dynamically partitioned free energy landscape. Proc Natl Acad Sci U S A 2008; 105:1489-93. [PMID: 18230738 PMCID: PMC2234171 DOI: 10.1073/pnas.0705707105] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Indexed: 11/18/2022] Open
Abstract
The B domain of staphylococcal protein A (BdpA) is a small helical protein that has been studied intensively in kinetics experiments and detailed computer simulations that include explicit water. The simulations indicate that BdpA needs to reorganize in crossing the transition barrier to facilitate folding its C-terminal helix (H3) onto the nucleus formed from helices H1 and H2. This process suggests frustration between two partially ordered forms of the protein, but recent varphi value measurements indicate that the transition structure is relatively constant over a broad range of temperatures. Here we develop a simplistic model to investigate the folding transition in which properties of the free energy landscape can be quantitatively compared with experimental data. The model is a continuation of the Muñoz-Eaton model to include the intermittency of contacts between structured parts of the protein, and the results compare variations in the landscape with denaturant and temperature to varphi value measurements and chevron plots of the kinetic rates. The topography of the model landscape (in particular, the feature of frustration) is consistent with detailed simulations even though variations in the varphi values are close to measured values. The transition barrier is smaller than indicated by the chevron data, but it agrees in order of magnitude with a similar alpha-carbon type of model. Discrepancies with the chevron plots are investigated from the point of view of solvent effects, and an approach is suggested to account for solvent participation in the model.
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Affiliation(s)
- Erik D. Nelson
- Howard Hughes Medical Institute and University of Texas Southwestern Medical Center, 6001 Forest Park Boulevard, Room ND10.124, Dallas, TX 75235-9050
| | - Nick V. Grishin
- Howard Hughes Medical Institute and University of Texas Southwestern Medical Center, 6001 Forest Park Boulevard, Room ND10.124, Dallas, TX 75235-9050
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14
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Weikl TR. Loop-closure principles in protein folding. Arch Biochem Biophys 2008; 469:67-75. [PMID: 17662688 DOI: 10.1016/j.abb.2007.06.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 06/20/2007] [Accepted: 06/22/2007] [Indexed: 10/23/2022]
Abstract
Simple theoretical concepts and models have been helpful to understand the folding rates and routes of single-domain proteins. As reviewed in this article, a physical principle that appears to underly these models is loop closure.
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Affiliation(s)
- Thomas R Weikl
- Max Planck Institute of Colloids and Interfaces, Department of Theory and Bio-Systems, 14424 Potsdam, Germany.
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15
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Cremades N, Sancho J, Freire E. The native-state ensemble of proteins provides clues for folding, misfolding and function. Trends Biochem Sci 2006; 31:494-6. [PMID: 16870449 DOI: 10.1016/j.tibs.2006.07.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Revised: 06/08/2006] [Accepted: 07/12/2006] [Indexed: 11/26/2022]
Abstract
The predominant equilibrium in proteins is not between native and unfolded states, it is between the native and multiple partially unfolded forms. Some of these partially unfolded forms can be energetically close to the native state and, therefore, have the potential to become appreciably populated. This could have an important role in protein function or misfolding diseases. The recent identification and characterization of the partially unfolded forms of apoflavodoxin furthers our understanding of their formation.
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Affiliation(s)
- Nunilo Cremades
- Department of Biochemistry and BIFI, University of Zaragoza, Zaragoza 50009, Spain
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