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Santhouse JR, Leung JMG, Chong LT, Horne WS. Effects of altered backbone composition on the folding kinetics and mechanism of an ultrafast-folding protein. Chem Sci 2024; 15:675-682. [PMID: 38179541 PMCID: PMC10763558 DOI: 10.1039/d3sc03976e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 12/02/2023] [Indexed: 01/06/2024] Open
Abstract
Sequence-encoded protein folding is a ubiquitous biological process that has been successfully engineered in a range of oligomeric molecules with artificial backbone chemical connectivity. A remarkable aspect of protein folding is the contrast between the rapid rates at which most sequences in nature fold and the vast number of conformational states possible in an unfolded chain with hundreds of rotatable bonds. Research efforts spanning several decades have sought to elucidate the fundamental chemical principles that dictate the speed and mechanism of natural protein folding. In contrast, little is known about how protein mimetic entities transition between an unfolded and folded state. Here, we report effects of altered backbone connectivity on the folding kinetics and mechanism of the B domain of Staphylococcal protein A (BdpA), an ultrafast-folding sequence. A combination of experimental biophysical analysis and atomistic molecular dynamics simulations performed on the prototype protein and several heterogeneous-backbone variants reveal the interplay among backbone flexibility, folding rates, and structural details of the transition state ensemble. Collectively, these findings suggest a significant degree of plasticity in the mechanisms that can give rise to ultrafast folding in the BdpA sequence and provide atomic level insights into how protein mimetic chains adopt an ordered folded state.
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Affiliation(s)
| | - Jeremy M G Leung
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Lillian T Chong
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - W Seth Horne
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
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2
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Santhouse JR, Leung JMG, Chong LT, Horne WS. Implications of the unfolded state in the folding energetics of heterogeneous-backbone protein mimetics. Chem Sci 2022; 13:11798-11806. [PMID: 36320921 PMCID: PMC9580521 DOI: 10.1039/d2sc04427g] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 09/19/2022] [Indexed: 12/28/2022] Open
Abstract
Sequence-encoded folding is the foundation of protein structure and is also possible in synthetic chains of artificial chemical composition. In natural proteins, the characteristics of the unfolded state are as important as those of the folded state in determining folding energetics. While much is known about folded structures adopted by artificial protein-like chains, corresponding information about the unfolded states of these molecules is lacking. Here, we report the consequences of altered backbone composition on the structure, stability, and dynamics of the folded and unfolded states of a compact helix-rich protein. Characterization through a combination of biophysical experiments and atomistic simulation reveals effects of backbone modification that depend on both the type of artificial monomers employed and where they are applied in sequence. In general, introducing artificial connectivity in a way that reinforces characteristics of the unfolded state ensemble of the prototype natural protein minimizes the impact of chemical changes on folded stability. These findings have implications in the design of protein mimetics and provide an atomically detailed picture of the unfolded state of a natural protein and artificial analogues under non-denaturing conditions. Biophysical experiments and atomistic simulation reveal impacts of protein backbone alteration on the ensemble that defines the unfolded state. These effects have implications on folded stability of protein mimetics.![]()
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Affiliation(s)
| | - Jeremy M. G. Leung
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15211, USA
| | - Lillian T. Chong
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15211, USA
| | - W. Seth Horne
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15211, USA
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3
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Protein Engineering Allows for Mild Affinity-based Elution of Therapeutic Antibodies. J Mol Biol 2018; 430:3427-3438. [DOI: 10.1016/j.jmb.2018.06.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 05/25/2018] [Accepted: 06/04/2018] [Indexed: 01/08/2023]
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4
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Goyal B, Srivastava KR, Durani S. Examination of the Effect of N-terminal Diproline and Charged Side Chains on the Stabilization of Helical Conformation in Alanine-based Short Peptides: A Molecular Dynamics Study. ChemistrySelect 2016. [DOI: 10.1002/slct.201601381] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Bhupesh Goyal
- Department of Chemistry; Indian Institute of Technology Bombay, Powai; Mumbai-400076 India
- Department of Chemistry; School of Basic and Applied Sciences; Sri Guru Granth Sahib World University, Fatehgarh; Sahib-140406, Punjab India
| | - Kinshuk Raj Srivastava
- Department of Chemistry; Indian Institute of Technology Bombay, Powai; Mumbai-400076 India
- Life Sciences Institute; University of Michigan; Ann Arbor, MI USA 48105
| | - Susheel Durani
- Department of Chemistry; Indian Institute of Technology Bombay, Powai; Mumbai-400076 India
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5
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MORISAKU T, ARAI S, YUI H. Dehydration-induced Initial Conformational Change of Hydrated Proteins Detected by the Changes in Vibrational Circular Dichroism Activity. ANAL SCI 2014; 30:961-9. [DOI: 10.2116/analsci.30.961] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Toshinori MORISAKU
- Graduate School of Chemical Science and Technology, Tokyo University of Science
| | - Sho ARAI
- Graduate School of Chemical Science and Technology, Tokyo University of Science
| | - Hiroharu YUI
- Graduate School of Chemical Science and Technology, Tokyo University of Science
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6
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Shao Q, Zhu W, Gao YQ. Robustness in Protein Folding Revealed by Thermodynamics Calculations. J Phys Chem B 2012; 116:13848-56. [DOI: 10.1021/jp307684h] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Qiang Shao
- Institute of Theoretical and
Computational Chemistry, College of Chemistry and Molecular Engineering,
Beijing National Laboratory of Molecular Sciences, Peking University, Beijing 100871, China
- Drug Discovery and Design Center,
Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203,
China
| | - Weiliang Zhu
- Drug Discovery and Design Center,
Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203,
China
| | - Yi Qin Gao
- Institute of Theoretical and
Computational Chemistry, College of Chemistry and Molecular Engineering,
Beijing National Laboratory of Molecular Sciences, Peking University, Beijing 100871, China
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7
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Lv C, Tan C, Qin M, Zou D, Cao Y, Wang W. Low folding cooperativity of HP35 revealed by single-molecule force spectroscopy and molecular dynamics simulation. Biophys J 2012; 102:1944-51. [PMID: 22768951 DOI: 10.1016/j.bpj.2012.03.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 03/08/2012] [Accepted: 03/14/2012] [Indexed: 10/28/2022] Open
Abstract
Some small proteins, such as HP35, fold at submicrosecond timescale with low folding cooperativity. Although these proteins have been extensively investigated, still relatively little is known about their folding mechanism. Here, using single-molecule force spectroscopy and steered molecule dynamics simulation, we study the unfolding of HP35 under external force. Our results show that HP35 unfolds at extremely low forces without a well-defined unfolding transition state. Subsequently, we probe the structure of unfolded HP35 using the persistence length obtained in the force spectroscopy. We found that the persistence length of unfolded HP35 is around 0.72 nm, >40% longer than typical unstructured proteins, suggesting that there are a significant amount of residual secondary structures in the unfolded HP35. Molecular dynamics simulation further confirmed this finding and revealed that many native contacts are preserved in HP35, even its two ends have been extended up to 8 nm. Our results therefore suggest that retaining a significant amount of secondary structures in the unfolded state of HP35 may be an efficient way to reduce the entropic cost for the formation of tertiary structure and increase the folding speed, although the folding cooperativity is compromised. Moreover, we anticipate that the methods we used in this work can be extended to the study of other proteins with complex folding behaviors and even intrinsically disordered ones.
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Affiliation(s)
- Chunmei Lv
- National Laboratory of Solid State Microstructure and Department of Physics, Nanjing University, Nanjing, People's Republic of China
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8
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Długosz M, Trylska J. Secondary structures of native and pathogenic huntingtin N-terminal fragments. J Phys Chem B 2011; 115:11597-608. [PMID: 21910495 DOI: 10.1021/jp206373g] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Huntington's disease is a neurodegenerative disorder caused by a polyglutamine (polyQ) expansion in the N-terminal fragment of the Huntingtin (Htt) protein. Structural properties of Htt N-terminal regions and the molecular mechanism leading to protein aggregation have not been fully explained yet. We performed all-atom replica exchange molecular dynamics to investigate the structures of Htt N-terminal parts with polyQ tracts of nonpathogenic and pathogenic lengths. The monomers were composed of the headpiece (17 N-terminal residues), a polyQ tract (polyQ(17) for native and polyQ(55) for pathogenic sequence), and a polyP(11) region, followed by 17 amino acids of mixed sequence. We found that corresponding regions in both fragments fold to similar secondary structures; the headpiece and polyQ stretch adopt mainly α-helical conformations, and polyP(11) forms the PP II-type helix. The native N-terminal fragment is more compact and stabilized by hydrophobic interactions between the surface of polyP(11) and the amphipathic helix of the headpiece. In the pathogenic fragment the headpiece is solvent exposed and does not interact with polyP(11). The predicted structure of the native N-terminal fragment agrees with the X-ray structure of the Htt first exon containing polyQ(17). The structure of the pathogenic fragment adheres to an aggregation model that is mediated by the Htt headpiece.
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Affiliation(s)
- Maciej Długosz
- Interdisciplinary Centre for Mathematical and Computational Modelling, University of Warsaw, Żwirki i Wigury 93, Warsaw 02-089, Poland.
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9
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Duan LL, Mei Y, Zhang D, Zhang QG, Zhang JZH. Folding of a helix at room temperature is critically aided by electrostatic polarization of intraprotein hydrogen bonds. J Am Chem Soc 2010; 132:11159-64. [PMID: 20698682 DOI: 10.1021/ja102735g] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report direct folding of a 17-residue helix protein (pdb:2I9M) by standard molecular dynamics simulation (single trajectory) at room temperature with implicit solvent. Starting from a fully extended structure, 2I9M successfully folds into the native conformation within 16 ns using adaptive hydrogen bond-specific charges to take into account the electrostatic polarization effect. Cluster analysis shows that conformations in the native state cluster have the highest population (78.4%) among all sampled conformations. Folding snapshots and the secondary structure analysis demonstrate that the folding of 2I9M begins at terminals and progresses toward the center. A plot of the free energy landscape indicates that there is no significant free energy barrier during folding, which explains the observed fast folding speed. For comparison, exactly the same molecular dynamics simulation but carried out under existing AMBER charges failed to fold 2I9M into native-like structures. The current study demonstrates that electrostatic polarization of intraprotein hydrogen bonding, which stabilizes the helix, is critical to the successful folding of 2I9m.
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Affiliation(s)
- Li L Duan
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, China
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10
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Meng W, Shan B, Tang Y, Raleigh DP. Native like structure in the unfolded state of the villin headpiece helical subdomain, an ultrafast folding protein. Protein Sci 2009; 18:1692-701. [PMID: 19598233 DOI: 10.1002/pro.152] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The villin headpiece subdomain, HP36, is the smallest naturally occurring protein that folds cooperatively. Its small size, rapid folding, and simple three-helix topology have made it an extremely popular system for computational studies of protein folding. The role of unfolded state structure in rapid folding is an area of active investigation, but relatively little is known about the properties of unfolded states under native conditions. A peptide fragment, HP21, which contains the first and second helices of HP36 has been shown to be a good model for structure in the unfolded state of the intact domain but a detailed description of the conformational propensities of HP21 is lacking and the balance between native and nonnative interactions is not known. A series of three-dimensional NMR experiments were performed on (13)C, (15)N-labeled HP21 to investigate in detail its conformational propensities. Analysis of (13)C(alpha), (13)C(beta), (13)CO chemical shifts, Deltadelta(13)C(alpha) - Deltadelta(13)C(beta) secondary shifts, the secondary structure propensity scores, NOEs, (15)N R(2) values and comparison of experimental chemical shifts with those of HP36 and with chemical shifts calculated using the SHIFTS and SHIFTX programs all indicate that there is significant native like structure in the HP21 ensemble, and thus by implication in the unfolded state of HP36.
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Affiliation(s)
- Wenli Meng
- Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA
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11
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Lei H, Wu C, Wang ZX, Zhou Y, Duan Y. Folding processes of the B domain of protein A to the native state observed in all-atom ab initio folding simulations. J Chem Phys 2008; 128:235105. [PMID: 18570534 DOI: 10.1063/1.2937135] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Reaching the native states of small proteins, a necessary step towards a comprehensive understanding of the folding mechanisms, has remained a tremendous challenge to ab initio protein folding simulations despite the extensive effort. In this work, the folding process of the B domain of protein A (BdpA) has been simulated by both conventional and replica exchange molecular dynamics using AMBER FF03 all-atom force field. Started from an extended chain, a total of 40 conventional (each to 1.0 micros) and two sets of replica exchange (each to 200.0 ns per replica) molecular dynamics simulations were performed with different generalized-Born solvation models and temperature control schemes. The improvements in both the force field and solvent model allowed successful simulations of the folding process to the native state as demonstrated by the 0.80 A C(alpha) root mean square deviation (RMSD) of the best folded structure. The most populated conformation was the native folded structure with a high population. This was a significant improvement over the 2.8 A C(alpha) RMSD of the best nativelike structures from previous ab initio folding studies on BdpA. To the best of our knowledge, our results demonstrate, for the first time, that ab initio simulations can reach the native state of BdpA. Consistent with experimental observations, including Phi-value analyses, formation of helix II/III hairpin was a crucial step that provides a template upon which helix I could form and the folding process could complete. Early formation of helix III was observed which is consistent with the experimental results of higher residual helical content of isolated helix III among the three helices. The calculated temperature-dependent profile and the melting temperature were in close agreement with the experimental results. The simulations further revealed that phenylalanine 31 may play critical to achieve the correct packing of the three helices which is consistent with the experimental observation. In addition to the mechanistic studies, an ab initio structure prediction was also conducted based on both the physical energy and a statistical potential. Based on the lowest physical energy, the predicted structure was 2.0 A C(alpha) RMSD away from the experimentally determined structure.
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Affiliation(s)
- Hongxing Lei
- UC Davis Genome Center and Department of Applied Science, University of California at Davis, One Shields Avenue, Davis, California 95616, USA
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12
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Gaikwad AV, Boffa V, ten Elshof JE, Rothenberg G. Cat-in-a-cup: facile separation of large homogeneous catalysts. Angew Chem Int Ed Engl 2008; 47:5407-10. [PMID: 18543258 DOI: 10.1002/anie.200801116] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Anil V Gaikwad
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands
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13
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Gaikwad A, Boffa V, ten Elshof J, Rothenberg G. Cat‐in‐a‐Cup: Facile Separation of Large Homogeneous Catalysts. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200801116] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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14
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Hu Z, Tang Y, Wang H, Zhang X, Lei M. Dynamics and cooperativity of Trp-cage folding. Arch Biochem Biophys 2008; 475:140-7. [DOI: 10.1016/j.abb.2008.04.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2008] [Revised: 04/11/2008] [Accepted: 04/19/2008] [Indexed: 11/26/2022]
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15
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Schlag EW, Sheu SY, Yang DY, Selzle HL, Lin SH. Distal charge transport in peptides. Angew Chem Int Ed Engl 2007; 46:3196-210. [PMID: 17372995 DOI: 10.1002/anie.200601623] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Biological systems often transport charges and reactive processes over substantial distances. Traditional models of chemical kinetics generally do not describe such extreme distal processes. In this Review, an atomistic model for a distal transport of information, which was specifically developed for peptides, is considered. Chemical reactivity is taken as the result of distal effects based on two-step bifunctional kinetics involving unique, very rapid motional properties of peptides in the subpicosecond regime. The bifunctional model suggests highly efficient transport of charge and reactivity in an isolated peptide over a substantial distance; conversely, a very low efficiency in a water environment was found. The model suggests ultrafast transport of charge and reactivity over substantial molecular distances in a peptide environment. Many such domains can be active in a protein.
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Affiliation(s)
- Edward W Schlag
- Institut für Physikalische und Theoretische Chemie, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany.
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16
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Schlag E, Sheu SY, Yang DY, Selzle H, Lin S. Distaler Ladungstransport in Peptiden. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200601623] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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17
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Lei H, Duan Y. Two-stage folding of HP-35 from ab initio simulations. J Mol Biol 2007; 370:196-206. [PMID: 17512537 PMCID: PMC2701201 DOI: 10.1016/j.jmb.2007.04.040] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 04/10/2007] [Accepted: 04/13/2007] [Indexed: 11/24/2022]
Abstract
Accurate ab initio simulation of protein folding is a critical step toward elucidation of protein-folding mechanisms. Here, we demonstrate highly accurate folding of the 35 residue villin headpiece subdomain (HP35) by all-atom molecular dynamics simulations using AMBER FF03 and the generalized-Born solvation model. In a set of 20 micros long simulations, the protein folded to the native state in multiple trajectories, with the lowest C(alpha) RMSD being 0.39 A for residues 2-34 (excluding residues 1 and 35). The native state had the highest population among all sampled conformations, and the center of most populated cluster had a C(alpha) RMSD of 1.63 A. Folding of this protein can be described as a two-stage process that followed a well-defined pathway. In the first stage, formation of helices II and III as a folding intermediate constituted the rate-limiting step and was initiated at a folding nucleus around residues Phe17 and Pro21. The folding intermediate further acted as a template that facilitated the folding and docking of helix I in the second stage. Detailed descriptions of the folding kinetics and the roles of key residues are presented.
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Affiliation(s)
- Hongxing Lei
- Genome Center and Department of Applied Science, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
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18
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Wang WZ, Lin T, Sun YC. Examination of the folding of a short alanine-based helical peptide with salt bridges using molecular dynamics simulation. J Phys Chem B 2007; 111:3508-14. [PMID: 17388513 DOI: 10.1021/jp067637a] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A molecular dynamics simulation of the folding of a short alanine-based helical peptide of 17 residues with three Glu...Lys (i, i + 4) salt bridge pairs, referred to as the AEK17 peptide, was carried out. The simulation gave an estimated simulation folding time of 2.5 ns, shorter than 12 ns for an alanine-based peptide of 16 residues with three Lys residues only, referred to as the AK16 peptide, simulated previously. After folded, the AEK17 peptide had a helical content of 77%, in excellent agreement with the experimentally determined value of 80%. An examination of the folding pathways of AEK17 indicated that the peptide proceeded via three-turn helix conformations more than the helix-turn-helix conformation in the folding pathways. An analysis of interactions indicated that the formation of hydrogen bonds between Lys residue side chains and backbone carbonyls is a major factor in the abundant conformation of the three-turn helix intermediate. The substitution of three Ala with Glu residues reduces the extent of hydrophobic interaction in alanine-based AK peptides with the result that the breaking of the interactions of Lys epsilon-NH3+(side chain)...C=O(backbone) is a major activation action for the AEK17 to achieve a complete fold, in contrast to the AK16 peptide, in which breaking non-native hydrophobic interaction is the rate-determining step.
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Affiliation(s)
- Wei-Zhou Wang
- Department of Chemistry, National Taiwan Normal University, 88, TingChow Road Section 4, Taipei 116, Taiwan
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19
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Lei H, Wu C, Liu H, Duan Y. Folding free-energy landscape of villin headpiece subdomain from molecular dynamics simulations. Proc Natl Acad Sci U S A 2007; 104:4925-30. [PMID: 17360390 PMCID: PMC1829241 DOI: 10.1073/pnas.0608432104] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
High-accuracy ab initio folding has remained an elusive objective despite decades of effort. To explore the folding landscape of villin headpiece subdomain HP35, we conducted two sets of replica exchange molecular dynamics for 200 ns each and three sets of conventional microsecond-long molecular dynamics simulations, using AMBER FF03 force field and a generalized-Born solvation model. The protein folded consistently to the native state; the lowest C(alpha)-rmsd from the x-ray structure was 0.46 A, and the C(alpha)- rmsd of the center of the most populated cluster was 1.78 A at 300 K. ab initio simulations have previously not reached this level. The folding landscape of HP35 can be partitioned into the native, denatured, and two intermediate-state regions. The native state is separated from the major folding intermediate state by a small barrier, whereas a large barrier exists between the major folding intermediate and the denatured states. The melting temperature T(m) = 339 K extracted from the heat-capacity profile was in close agreement with the experimentally derived T(m) = 342 K. A comprehensive picture of the kinetics and thermodynamics of HP35 folding emerges when the results from replica exchange and conventional molecular dynamics simulations are combined.
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Affiliation(s)
- Hongxing Lei
- Genome Center and Department of Applied Science, University of California, Davis, CA 95616
| | - Chun Wu
- Genome Center and Department of Applied Science, University of California, Davis, CA 95616
| | - Haiguang Liu
- Genome Center and Department of Applied Science, University of California, Davis, CA 95616
| | - Yong Duan
- Genome Center and Department of Applied Science, University of California, Davis, CA 95616
- *To whom correspondence should be addressed. E-mail:
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20
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Jagielska A, Scheraga HA. Influence of temperature, friction, and random forces on folding of the B-domain of staphylococcal protein A: All-atom molecular dynamics in implicit solvent. J Comput Chem 2007; 28:1068-82. [PMID: 17279497 DOI: 10.1002/jcc.20631] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The influences of temperature, friction, and random forces on the folding of protein A have been analyzed. A series of all-atom molecular dynamics folding simulations with the Amber ff99 potential and Generalized Born solvation, starting from the fully extended chain, were carried out for temperatures from 300 to 500 K, using (a) the Berendsen thermostat (with no explicit friction or random forces) and (b) Langevin dynamics (with friction and stochastic forces explicitly present in the system). The simulation temperature influences the relative time scale of the major events on the folding pathways of protein A. At lower temperatures, helix 2 folds significantly later than helices 1 and 3. However, with increasing temperature, the folding time of helix 2 approaches the folding times of helices 1 and 3. At lower temperatures, the complete formation of secondary and tertiary structure is significantly separated in time whereas, at higher temperatures, they occur simultaneously. These results suggest that some earlier experimental and theoretical observations of folding events, e.g., the order of helix formation, could depend on the temperature used in those studies. Therefore, the differences in temperature used could be one of the reasons for the discrepancies among published experimental and computational studies of the folding of protein A. Friction and random forces do not change the folding pathway that was observed in the simulations with the Berendsen thermostat, but their explicit presence in the system extends the folding time of protein A.
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Affiliation(s)
- Anna Jagielska
- Baker Laboratory of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA
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21
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Tang Y, Goger MJ, Raleigh DP. NMR Characterization of a Peptide Model Provides Evidence for Significant Structure in the Unfolded State of the Villin Headpiece Helical Subdomain. Biochemistry 2006; 45:6940-6. [PMID: 16734429 DOI: 10.1021/bi052484n] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The villin headpiece subdomain (HP36) is the smallest naturally occurring protein that folds cooperatively. The protein folds on a microsecond time scale. Its small size and very rapid folding have made it a popular target for biophysical studies of protein folding. Temperature-dependent one-dimensional (1D) NMR studies of the full-length protein together with CD and 1D NMR studies of the 21-residue peptide fragment (HP21) derived from HP36 have shown that there is significant structure in the unfolded state of HP36 and have demonstrated that HP21 is a good model of these interactions. Here, we characterized the model peptide HP21 in detail by two-dimensional NMR. Strongly upfield shifted C(alpha) protons, the magnitude of the 3J(NH,alpha) coupling constants, and the pattern of backbone-backbone and backbone-side chain NOEs indicate that the ensemble of structures populated by HP21 contains alpha-helical structure and native as well as non-native hydrophobic contacts. The hydrogen-bonded secondary structure inferred from the NOEs is, however, not sufficient to confer significant protection against amide H-D exchange. These studies indicate that there is significant secondary structure and hydrophobic clustering in the unfolded state of HP36. The implications for the folding of HP36 are discussed.
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Affiliation(s)
- Yuefeng Tang
- Department of Chemistry, State University of New York, Stony Brook, New York 11790-3400, USA
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