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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.
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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
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2
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Lindorff-Larsen K. Dissecting the statistical properties of the linear extrapolation method of determining protein stability. Protein Eng Des Sel 2020; 32:471-479. [DOI: 10.1093/protein/gzaa010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/18/2020] [Accepted: 04/19/2020] [Indexed: 11/13/2022] Open
Abstract
AbstractThe linear extrapolation method to determine protein stability from denaturant-induced unfolding experiments is based on the observation that the free energy of unfolding is often a linear function of the denaturant concentration. The value in the absence of denaturant is then estimated by extrapolation from this linear relationship. Parameters and their confidence intervals are typically estimated by nonlinear least-squares regression. We have compared different methods for calculating confidence intervals and found that a simple method based on linear theory gives accurate results. We have also compared three different parameterizations of the linear extrapolation method and show that the most commonly used form is problematic since the stability and m-value are correlated in the nonlinear least-squares analysis. Parameter correlation can in some cases causes problems in the estimation of confidence intervals and regions and should be avoided when possible. Two alternative parameterizations show much less correlation between parameters.
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Affiliation(s)
- Kresten Lindorff-Larsen
- Structural Biology and NMR Laboratory & Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark
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3
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Kim SG, Chen YJ, Falzon L, Baum J, Inouye M. Mimicking cotranslational folding of prosubtilisin E in vitro. J Biochem 2020; 167:473-482. [DOI: 10.1093/jb/mvaa004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 12/10/2019] [Indexed: 12/12/2022] Open
Abstract
AbstractNascent polypeptides are synthesized on ribosomes starting at the N-terminus and simultaneously begin to fold during translation. We constructed N-terminal fragments of prosubtilisin E containing an intramolecular chaperone (IMC) at N-terminus to mimic cotranslational folding intermediates of prosubtilisin. The IMC-fragments of prosubtilisin exhibited progressive enhancement of their secondary structures and thermostabilities with increasing polypeptide length. However, even the largest IMC-fragment with 72 residues truncated from the C-terminus behaved as a molten globule, indicating the requirement of the C-terminal region to have a stable tertiary structure. Furthermore, truncation of the IMC in the IMC-fragments resulted in aggregation, suggesting that the IMC plays a crucial role to prevent misfolding and aggregation of cotranslational folding intermediates during translation of prosubtilisin polypeptide.
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Affiliation(s)
- Sung-Gun Kim
- Department of Biomedical Science, U1 University, Chungbuk 29131, Republic of Korea
| | - Yu-Jen Chen
- Department of Biochemistry and Cell Biology, Center for Advanced Biotechnology and Medicine (CABM), Rutgers-Robert Wood Johnson Medical School, 679 Hoes Lane, Piscataway, NJ 08854, USA
| | - Liliana Falzon
- Department of Biochemistry and Cell Biology, Center for Advanced Biotechnology and Medicine (CABM), Rutgers-Robert Wood Johnson Medical School, 679 Hoes Lane, Piscataway, NJ 08854, USA
| | - Jean Baum
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Masayori Inouye
- Department of Biochemistry and Cell Biology, Center for Advanced Biotechnology and Medicine (CABM), Rutgers-Robert Wood Johnson Medical School, 679 Hoes Lane, Piscataway, NJ 08854, USA
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4
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Petrosino M, Pasquo A, Novak L, Toto A, Gianni S, Mantuano E, Veneziano L, Minicozzi V, Pastore A, Puglisi R, Capriotti E, Chiaraluce R, Consalvi V. Characterization of human frataxin missense variants in cancer tissues. Hum Mutat 2019; 40:1400-1413. [PMID: 31074541 PMCID: PMC6744310 DOI: 10.1002/humu.23789] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 04/17/2019] [Accepted: 05/06/2019] [Indexed: 12/19/2022]
Abstract
Human frataxin is an iron-binding protein involved in the mitochondrial iron-sulfur (Fe-S) clusters assembly, a process fundamental for the functional activity of mitochondrial proteins. Decreased level of frataxin expression is associated with the neurodegenerative disease Friedreich ataxia. Defective function of frataxin may cause defects in mitochondria, leading to increased tumorigenesis. Tumor-initiating cells show higher iron uptake, a decrease in iron storage and a reduced Fe-S clusters synthesis and utilization. In this study, we selected, from COSMIC database, the somatic human frataxin missense variants found in cancer tissues p.D104G, p.A107V, p.F109L, p.Y123S, p.S161I, p.W173C, p.S181F, and p.S202F to analyze the effect of the single amino acid substitutions on frataxin structure, function, and stability. The spectral properties, the thermodynamic and the kinetic stability, as well as the molecular dynamics of the frataxin missense variants found in cancer tissues point to local changes confined to the environment of the mutated residues. The global fold of the variants is not altered by the amino acid substitutions; however, some of the variants show a decreased stability and a decreased functional activity in comparison with that of the wild-type protein.
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Affiliation(s)
- Maria Petrosino
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”. Sapienza University of Rome, Rome, Italy
- Current address: IRCCS Istituto Neurologico Carlo Besta, Milano, Italia
- European Brain Research Institute-Fondazione Rita Levi Montalcini, Roma, Italia
| | - Alessandra Pasquo
- ENEA CR Frascati, Diagnostics and Metrology Laboratory,FSN-TECFIS-DIM, Frascati, Italy
| | - Leonore Novak
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”. Sapienza University of Rome, Rome, Italy
| | - Angelo Toto
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”. Sapienza University of Rome, Rome, Italy
- Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, Rome, Italy
| | - Stefano Gianni
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”. Sapienza University of Rome, Rome, Italy
- Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, Rome, Italy
| | - Elide Mantuano
- Institute of Translational Pharmacology, CNR, Rome, Italy
| | | | - Velia Minicozzi
- INFN and Department of Physics, University of Rome Tor Vergata, Rome, Italy
| | - Annalisa Pastore
- The Wohl Institute, King’s College London, London, United Kingdom
| | - Rita Puglisi
- The Wohl Institute, King’s College London, London, United Kingdom
| | - Emidio Capriotti
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Bologna, Italy
| | - Roberta Chiaraluce
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”. Sapienza University of Rome, Rome, Italy
| | - Valerio Consalvi
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”. Sapienza University of Rome, Rome, Italy
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5
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Janati-Fard F, Housaindokht MR, Monhemi H, Nakhaeipour A. How a multimeric macromolecule is affected by divalent salts? Experimental and simulation study. Int J Biol Macromol 2017; 106:284-292. [PMID: 28782614 DOI: 10.1016/j.ijbiomac.2017.08.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 07/29/2017] [Accepted: 08/02/2017] [Indexed: 10/19/2022]
Abstract
Salts exist in any cell and living organism in contact with biological macromolecules. How these salts affect biomolecules such as enzyme is important from both basic sciences and practical technologies. It was observed that divalent salts can change structure and function of protein at higher concentrations. Here, we investigated the effect of divalent salt on the behavior of a multimeric enzyme. We treated glucose oxidase as dimer-active enzyme in different CaCl2 concentration and seen that the enzyme become inactive at high concentration of salt. These experimental results are in agreement with recently published researches. To find a possible mechanism, a series of molecular dynamics simulation of the enzyme were performed at different salt concentration. According to the MD simulation, the conformational changes at the active site and FAD-binding site support the hypothesis of enzyme inactivation at high CaCl2 concentration. MD simulations also showed that enzyme has an unstable conformation at higher salt concentration which is in agreement with our experimental data. Detailed structural properties of the enzyme have been analyzed under different conditions. To the best of our knowledge, this is the first study that bears detailed structural mechanism about the salt effects on multimeric macromolecules.
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Affiliation(s)
- Fatemeh Janati-Fard
- Biophysical Chemistry Laboratory, Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
| | - Mohammad R Housaindokht
- Biophysical Chemistry Laboratory, Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran; Research and Technology Center of Biomolecules, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran.
| | - Hassan Monhemi
- Research and Technology Center of Biomolecules, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
| | - Ali Nakhaeipour
- Biophysical Chemistry Laboratory, Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
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6
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Lori L, Pasquo A, Lori C, Petrosino M, Chiaraluce R, Tallant C, Knapp S, Consalvi V. Effect of BET Missense Mutations on Bromodomain Function, Inhibitor Binding and Stability. PLoS One 2016; 11:e0159180. [PMID: 27403962 PMCID: PMC4942050 DOI: 10.1371/journal.pone.0159180] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 06/28/2016] [Indexed: 02/03/2023] Open
Abstract
Lysine acetylation is an important epigenetic mark regulating gene transcription and chromatin structure. Acetylated lysine residues are specifically recognized by bromodomains, small protein interaction modules that read these modification in a sequence and acetylation dependent way regulating the recruitment of transcriptional regulators and chromatin remodelling enzymes to acetylated sites in chromatin. Recent studies revealed that bromodomains are highly druggable protein interaction domains resulting in the development of a large number of bromodomain inhibitors. BET bromodomain inhibitors received a lot of attention in the oncology field resulting in the rapid translation of early BET bromodomain inhibitors into clinical studies. Here we investigated the effects of mutations present as polymorphism or found in cancer on BET bromodomain function and stability and the influence of these mutants on inhibitor binding. We found that most BET missense mutations localize to peripheral residues in the two terminal helices. Crystal structures showed that the three dimensional structure is not compromised by these mutations but mutations located in close proximity to the acetyl-lysine binding site modulate acetyl-lysine and inhibitor binding. Most mutations affect significantly protein stability and tertiary structure in solution, suggesting new interactions and an alternative network of protein-protein interconnection as a consequence of single amino acid substitution. To our knowledge this is the first report studying the effect of mutations on bromodomain function and inhibitor binding.
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Affiliation(s)
- Laura Lori
- Department of Biochemical Sciences “A. Rossi Fanelli”, Sapienza University of Rome, Rome, Italy
| | | | - Clorinda Lori
- Department of Biochemical Sciences “A. Rossi Fanelli”, Sapienza University of Rome, Rome, Italy
| | - Maria Petrosino
- Department of Biochemical Sciences “A. Rossi Fanelli”, Sapienza University of Rome, Rome, Italy
| | - Roberta Chiaraluce
- Department of Biochemical Sciences “A. Rossi Fanelli”, Sapienza University of Rome, Rome, Italy
- * E-mail:
| | - Cynthia Tallant
- Nuffield Department of Clinical Medicine, Structural Genomics Consortium and Target Discovery Institute, University of Oxford, Oxford, United Kingdom
| | - Stefan Knapp
- Nuffield Department of Clinical Medicine, Structural Genomics Consortium and Target Discovery Institute, University of Oxford, Oxford, United Kingdom
| | - Valerio Consalvi
- Department of Biochemical Sciences “A. Rossi Fanelli”, Sapienza University of Rome, Rome, Italy
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7
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Using the folding landscapes of proteins to understand protein function. Curr Opin Struct Biol 2016; 36:67-74. [PMID: 26812092 DOI: 10.1016/j.sbi.2016.01.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 12/31/2015] [Accepted: 01/06/2016] [Indexed: 11/20/2022]
Abstract
Proteins fold on a biologically-relevant timescale because of a funnel-shaped energy landscape. This landscape is sculpted through evolution by selecting amino-acid sequences that stabilize native interactions while suppressing stable non-native interactions that occur during folding. However, there is strong evolutionary selection for functional residues and these cannot be chosen to optimize folding. Their presence impacts the folding energy landscape in a variety of ways. Here, we survey the effects of functional residues on folding by providing several examples. We then review how such effects can be detected computationally and be used as assays for protein function. Overall, an understanding of how functional residues modulate folding should provide insights into the design of natural proteins and their homeostasis.
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8
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Naganathan AN, Sanchez-Ruiz JM, Munshi S, Suresh S. Are Protein Folding Intermediates the Evolutionary Consequence of Functional Constraints? J Phys Chem B 2015; 119:1323-33. [DOI: 10.1021/jp510342m] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Athi N. Naganathan
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India
| | - Jose M. Sanchez-Ruiz
- Departamento de Quimica Fisica,
Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain
| | - Sneha Munshi
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India
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9
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Aghera N, Udgaonkar JB. The Utilization of Competing Unfolding Pathways of Monellin Is Dictated by Enthalpic Barriers. Biochemistry 2013; 52:5770-9. [DOI: 10.1021/bi400688w] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Nilesh Aghera
- National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bangalore 560065,
India
| | - Jayant B. Udgaonkar
- National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bangalore 560065,
India
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10
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Udgaonkar JB. Polypeptide chain collapse and protein folding. Arch Biochem Biophys 2013; 531:24-33. [DOI: 10.1016/j.abb.2012.10.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 10/01/2012] [Accepted: 10/08/2012] [Indexed: 12/11/2022]
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11
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Dasgupta A, Udgaonkar JB. Transient Non-Native Burial of a Trp Residue Occurs Initially during the Unfolding of a SH3 Domain. Biochemistry 2012; 51:8226-34. [DOI: 10.1021/bi3008627] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Amrita Dasgupta
- National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bangalore 560065,
India
| | - Jayant B. Udgaonkar
- National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bangalore 560065,
India
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12
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Aghera N, Earanna N, Udgaonkar JB. Equilibrium unfolding studies of monellin: the double-chain variant appears to be more stable than the single-chain variant. Biochemistry 2011; 50:2434-44. [PMID: 21351752 DOI: 10.1021/bi101955f] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To improve our understanding of the contributions of different stabilizing interactions to protein stability, including that of residual structure in the unfolded state, the small sweet protein monellin has been studied in both its two variant forms, the naturally occurring double-chain variant (dcMN) and the artificially created single-chain variant (scMN). Equilibrium guanidine hydrochloride-induced unfolding studies at pH 7 show that the standard free energy of unfolding, ΔG°(U), of dcMN to unfolded chains A and B and its dependence on guanidine hydrochloride (GdnHCl) concentration are both independent of protein concentration, while the midpoint of unfolding has an exponential dependence on protein concentration. Hence, the unfolding of dcMN like that of scMN can be described as two-state unfolding. The free energy of dissociation, ΔG°(d), of the two free chains, A and B, from dcMN, as measured by equilibrium binding studies, is significantly lower than ΔG°(U), apparently because of the presence of residual structure in free chain B. The value of ΔG°(U), at the standard concentration of 1 M, is found to be ∼5.5 kcal mol(-1) higher for dcMN than for scMN in the range from pH 4 to 9, over which unfolding appears to be two-state. Hence, dcMN appears to be more stable than scMN. It seems that unfolded scMN is stabilized by residual structure that is absent in unfolded dcMN and/or that native scMN is destabilized by strain that is relieved in native dcMN. The value of ΔG°(U) for both protein variants decreases with an increase in pH from 4 to 9, apparently because of the thermodynamic coupling of unfolding to the protonation of a buried carboxylate side chain whose pK(a) shifts from 4.5 in the unfolded state to 9 in the native state. Finally, it is shown that although the thermodynamic stabilities of dcMN and scMN are very different, their kinetic stabilities with respect to unfolding in GdnHCl are very similar.
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Affiliation(s)
- Nilesh Aghera
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
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13
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Direct evidence for a dry molten globule intermediate during the unfolding of a small protein. Proc Natl Acad Sci U S A 2009; 106:12289-94. [PMID: 19617531 DOI: 10.1073/pnas.0905744106] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Little is known about how proteins begin to unfold. In particular, how and when water molecules penetrate into the protein interior during unfolding, thereby enabling the dissolution of specific structure, is poorly understood. The hypothesis that the native state expands initially into a dry molten globule, in which tight packing interactions are broken, but whose hydrophobic core has not expanded sufficiently to be able to absorb water molecules, has very little experimental support. Here, we report our analysis of the earliest observable events during the unfolding of single chain monellin (MNEI), a small plant protein. Far- and near-UV circular dichroism measurements of GdnHCl-induced unfolding indicate that a molten globule intermediate forms initially, before the major slow unfolding reaction commences. Steady-state fluorescence resonance energy transfer measurements show that the C-terminal end of the single helix of MNEI initially moves rapidly away from the single tryptophan residue that is close to the N-terminal end of the helix. The average end-to-end distance of the protein also expands during unfolding to the molten globule intermediate. At this time, water has yet to penetrate the protein core, according to the evidence from intrinsic tryptophan fluorescence and 8-anilino-1-naphthalenesulfonic acid fluorescence-monitored kinetic unfolding measurements. Our results therefore provide direct evidence for a dry molten globule intermediate at the initial stage of unfolding. Our results further suggest that the structural transition between the native and dry molten globule states could be an all-or-none transition, whereas further swelling of the globule appears to occur gradually.
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14
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Hofmann H, Golbik RP, Ott M, Hübner CG, Ulbrich-Hofmann R. Coulomb Forces Control the Density of the Collapsed Unfolded State of Barstar. J Mol Biol 2008; 376:597-605. [DOI: 10.1016/j.jmb.2007.11.083] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Revised: 11/26/2007] [Accepted: 11/27/2007] [Indexed: 10/22/2022]
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15
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Abstract
Measurements of protein folding and thermodynamic stability provide insight into the forces and energetics that determine structure, and can inform on protein domain organization, interdomain interactions, and effects of mutations on structure. This chapter describes methods, theory, and data analysis for the most accessible means to determine the thermodynamics of protein folding: chemical denaturation. Topics include overall features of the folding reaction, advances in instrumentation, optimization of reagent purity, mechanistic models for analysis, and statistical and structural interpretation of fitted thermodynamic parameters. Examples in which stability measurements have provided insight into structure and function will be taken from studies in the author's laboratory on the Notch signaling pathway. It is hoped that this chapter will enable molecular, cell, and structural biologists to make precise measurements of protein stability, and will also provide a strong foundation for biophysics students who wish to undertake experimental studies of protein folding.
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16
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Jha SK, Udgaonkar JB. Exploring the Cooperativity of the Fast Folding Reaction of a Small Protein Using Pulsed Thiol Labeling and Mass Spectrometry. J Biol Chem 2007; 282:37479-91. [DOI: 10.1074/jbc.m706714200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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17
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Chiaraluce R, Florio R, Angelaccio S, Gianese G, van Lieshout JFT, van der Oost J, Consalvi V. Tertiary structure in 7.9 m guanidinium chloride − the role of Glu53 and Asp287 in Pyrococcus furiosus endo-β-1,3-glucanase. FEBS J 2007; 274:6167-79. [DOI: 10.1111/j.1742-4658.2007.06137.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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18
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Chiaraluce R, Florio R, Angelaccio S, Gianese G, van Lieshout JFT, van der Oost J, Consalvi V. Tertiary structure in 7.9 m guanidinium chloride − the role of Glu53 and Asp287 in Pyrococcus furiosus endo-β-1,3-glucanase. FEBS J 2007. [DOI: 10.1111/j.1742-4658.2007.6137.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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19
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Saxena AM, Udgaonkar JB, Krishnamoorthy G. Characterization of Intra-molecular Distances and Site-specific Dynamics in Chemically Unfolded Barstar: Evidence for Denaturant-dependent Non-random Structure. J Mol Biol 2006; 359:174-89. [PMID: 16603185 DOI: 10.1016/j.jmb.2006.03.013] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2005] [Revised: 03/02/2006] [Accepted: 03/08/2006] [Indexed: 11/22/2022]
Abstract
The structure and dynamics of the unfolded form of a protein are expected to play critical roles in determining folding pathways. In this study, the urea and guanidine hydrochloride (GdnHCl)-unfolded forms of the small protein barstar were explored by time-resolved fluorescence techniques. Barstar was labeled specifically with thionitrobenzoate (TNB), by coupling it to the thiol side-chain of a cysteine residue at one of the following positions on the sequence: 14, 25, 40, 42, 62, 82 and 89, in single cysteine-containing mutant proteins. Seven intra-molecular distances (R(DA)) under unfolding conditions were estimated from measurements of time-resolved fluorescence resonance energy transfer between the donor Trp53 and the non-fluorescent acceptor TNB coupled to one of the seven cysteine side-chains. The unfolded protein chain expands with an increase in the concentration of the denaturants. The extent of expansion was found to be non-uniform, with different intra-molecular distances expanding to different extents. In general, shorter distances were found to expand less when compared to longer spans. The extent of expansion was higher in the case of GdnHCl when compared to urea. A comparison of the measured values of R(DA) with those derived from a model based on excluded volume, revealed that while shorter spans showed good agreement, the experimental values of R(DA) of longer spans were smaller when compared to the theoretical values. Sequence-specific flexibility of the polypeptide was determined by time-resolved fluorescence anisotropy decay measurements on acrylodan or 1,5-IAEDANS labeled single cysteine-containing proteins under unfolding conditions. Rotational dynamics derived from these measurements indicated that the level of flexibility increased with increase in the concentration of denaturants and showed a graded increase towards the C-terminal end. Taken together, these results appear to indicate the presence of specific non-random coil structures and show that the deviation from random coil structure is different for the two denaturants.
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Affiliation(s)
- Anoop M Saxena
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
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20
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Fujimoto Y, Ikeuchi H, Tada T, Oyama H, Oda K, Kunugi S. Synergetic effects of pressure and chemical denaturant on protein unfolding: stability of a serine-type carboxyl protease, kumamolisin. BIOCHIMICA ET BIOPHYSICA ACTA 2006; 1764:364-71. [PMID: 16478682 DOI: 10.1016/j.bbapap.2005.12.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Revised: 12/10/2005] [Accepted: 12/13/2005] [Indexed: 11/25/2022]
Abstract
Kumamolisin, a serine carboxyl proteinase, is very stable and hardly denatured by single perturbation of a chemical denaturant (urea), pressure (<500 MPa) or temperature (<65 degrees C). In order to investigate the cooperative effects of these three denaturing agents, DSC, CD, intrinsic fluorescence, and fourth derivative UV absorbance were measured under various conditions. By application of pressure to kumamolisin in 8 M urea solution, substantial red-shift in the center of fluorescence emission spectral mass was observed, and the corresponding blue-shift was observed for two major peaks in fourth derivative UV absorbance, under the similar urea-containing conditions. The denaturation curves were analyzed on the basis of a simple two-state model in order to obtain thermodynamic parameters (DeltaV, DeltaG, and m values), and the combined effects of denaturing agents are discussed, with the special interest in the large cavity and neighboring Trp residue in kumamolisin.
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Affiliation(s)
- Yasunori Fujimoto
- Department of Polymer Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo, 606-8585, Japan
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Trefethen JM, Pace CN, Scholtz JM, Brems DN. Charge-charge interactions in the denatured state influence the folding kinetics of ribonuclease Sa. Protein Sci 2005; 14:1934-8. [PMID: 15937282 PMCID: PMC2253365 DOI: 10.1110/ps.051401905] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Gaining a better understanding of the denatured state ensemble of proteins is important for understanding protein stability and the mechanism of protein folding. We studied the folding kinetics of ribonuclease Sa (RNase Sa) and a charge-reversal variant (D17R). The refolding kinetics are similar, but the unfolding rate constant is 10-fold greater for the variant. This suggests that charge-charge interactions in the denatured state and the transition state ensembles are more favorable in the variant than in RNase Sa, and shows that charge-charge interactions can influence the kinetics and mechanism of protein folding.
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Affiliation(s)
- Jared M Trefethen
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-1114, USA
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