1
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Becht DC, Leavens MJ, Zeng B, Rothfuss MT, Briknarová K, Bowler BE. Residual Structure in the Denatured State of the Fast-Folding UBA(1) Domain from the Human DNA Excision Repair Protein HHR23A. Biochemistry 2022; 61:767-784. [PMID: 35430812 PMCID: PMC9150713 DOI: 10.1021/acs.biochem.2c00011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structure of the first ubiquitin-associated domain from HHR23A, UBA(1), was determined by X-ray crystallography at a 1.60 Å resolution, and its stability, folding kinetics, and residual structure under denaturing conditions have been investigated. The concentration dependence of thermal denaturation and size-exclusion chromatography indicate that UBA(1) is monomeric. Guanidine hydrochloride (GdnHCl) denaturation experiments reveal that the unfolding free energy, ΔGu°'(H2O), of UBA(1) is 2.4 kcal mol-1. Stopped-flow folding kinetics indicates sub-millisecond folding with only proline isomerization phases detectable at 25 °C. The full folding kinetics are observable at 4 °C, yielding a folding rate constant, kf, in the absence of a denaturant of 13,000 s-1 and a Tanford β-value of 0.80, consistent with a compact transition state. Evaluation of the secondary structure via circular dichroism shows that the residual helical structure in the denatured state is replaced by polyproline II structure as the GdnHCl concentration increases. Analysis of NMR secondary chemical shifts for backbone 15NH, 13CO, and 13Cα atoms between 4 and 7 M GdnHCl shows three islands of residual helical secondary structure that align in sequence with the three native-state helices. Extrapolation of the NMR data to 0 M GdnHCl demonstrates that helical structure would populate to 17-33% in the denatured state under folding conditions. Comparison with NMR data for a peptide corresponding to helix 1 indicates that this helix is stabilized by transient tertiary interactions in the denatured state of UBA(1). The high helical content in the denatured state, which is enhanced by transient tertiary interactions, suggests a diffusion-collision folding mechanism.
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Affiliation(s)
- Dustin C. Becht
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Moses J. Leavens
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Baisen Zeng
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Michael T. Rothfuss
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Klára Briknarová
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Bruce E. Bowler
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
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2
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Leavens MJ, Spang LE, Cherney MM, Bowler BE. Denatured State Conformational Biases in Three-Helix Bundles Containing Divergent Sequences Localize near Turns and Helix Capping Residues. Biochemistry 2021; 60:3071-3085. [PMID: 34606713 PMCID: PMC8751257 DOI: 10.1021/acs.biochem.1c00400] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rhodopseudomonas palustris cytochrome c', a four-helix bundle, and the second ubiquitin-associated domain, UBA(2), a three-helix bundle from the human homologue of yeast Rad23, HHR23A, deviate from random coil behavior under denaturing conditions in a fold-specific manner. The random coil deviations in each of these folds occur near interhelical turns and loops in their tertiary structures. Here, we examine an additional three-helix bundle with an identical fold to UBA(2), but a highly divergent sequence, the first ubiquitin-associated domain, UBA(1), of HHR23A. We use histidine-heme loop formation methods, employing eight single histidine variants, to probe for denatured state conformational bias of a UBA(1) domain fused to the N-terminus of iso-1-cytochrome c (iso-1-Cytc). Guanidine hydrochloride (GuHCl) denaturation shows that the iso-1-Cytc domain unfolds first, followed by the UBA(1) domain. Denatured state (4 and 6 M GuHCl) histidine-heme loop formation studies show that as the size of the histidine-heme loop increases, loop stability decreases, as expected for the Jacobson-Stockmayer relationship. However, loops formed with His35, His31, and His15, of UBA(1), are 0.6-1.1 kcal/mol more stable than expected from the Jacobson-Stockmayer relationship, confirming the importance of deviations of the denatured state from random coil behavior near interhelical turns of helical domains for facilitating folding to the correct topology. For UBA(1) and UBA(2), hydrophobic clusters on either side of the turns partially explain deviations from random coil behavior; however, helix capping also appears to be important.
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Affiliation(s)
- Moses J. Leavens
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Lisa E. Spang
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Melisa M. Cherney
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Bruce E. Bowler
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
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3
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Rösner HI, Caldarini M, Potel G, Malmodin D, Vanoni MA, Aliverti A, Broglia RA, Kragelund BB, Tiana G. The denatured state of HIV-1 protease under native conditions. Proteins 2021; 90:96-109. [PMID: 34312913 PMCID: PMC9290662 DOI: 10.1002/prot.26189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/21/2021] [Accepted: 07/22/2021] [Indexed: 12/01/2022]
Abstract
The denatured state of several proteins has been shown to display transient structures that are relevant for folding, stability, and aggregation. To detect them by nuclear magnetic resonance (NMR) spectroscopy, the denatured state must be stabilized by chemical agents or changes in temperature. This makes the environment different from that experienced in biologically relevant processes. Using high‐resolution heteronuclear NMR spectroscopy, we have characterized several denatured states of a monomeric variant of HIV‐1 protease, which is natively structured in water, induced by different concentrations of urea, guanidinium chloride, and acetic acid. We have extrapolated the chemical shifts and the relaxation parameters to the denaturant‐free denatured state at native conditions, showing that they converge to the same values. Subsequently, we characterized the conformational properties of this biologically relevant denatured state under native conditions by advanced molecular dynamics simulations and validated the results by comparison to experimental data. We show that the denatured state of HIV‐1 protease under native conditions displays rich patterns of transient native and non‐native structures, which could be of relevance to its guidance through a complex folding process.
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Affiliation(s)
- Heike I Rösner
- BRIC, University of Copenhagen, Copenhagen N, Denmark.,Structural Biology and NMR Laboratory (SBiNlab), Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Martina Caldarini
- Department of Physics, Università degli Studi di Milano and INFN, Milan, Italy
| | - Gregory Potel
- Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Daniel Malmodin
- Structural Biology and NMR Laboratory (SBiNlab), Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Maria A Vanoni
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | | | - Ricardo A Broglia
- Department of Physics, Università degli Studi di Milano and INFN, Milan, Italy.,Niels Bohr Institutet, University of Copenhagen, Copenhagen Ø, Denmark
| | - Birthe B Kragelund
- Structural Biology and NMR Laboratory (SBiNlab), Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Guido Tiana
- Department of Physics, Università degli Studi di Milano and INFN, Milan, Italy.,Center for Complexity and Biosystems, Università degli Studi di Milano, Milan, Italy
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4
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Sonar P, Bellucci L, Mossa A, Heidarsson PO, Kragelund BB, Cecconi C. Effects of Ligand Binding on the Energy Landscape of Acyl-CoA-Binding Protein. Biophys J 2020; 119:1821-1832. [PMID: 33080224 PMCID: PMC7677128 DOI: 10.1016/j.bpj.2020.09.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 08/14/2020] [Accepted: 09/08/2020] [Indexed: 12/19/2022] Open
Abstract
Binding of ligands is often crucial for function yet the effects of ligand binding on the mechanical stability and energy landscape of proteins are incompletely understood. Here, we use a combination of single-molecule optical tweezers and MD simulations to investigate the effect of ligand binding on the energy landscape of acyl-coenzyme A (CoA)-binding protein (ACBP). ACBP is a topologically simple and highly conserved four-α-helix bundle protein that acts as an intracellular transporter and buffer for fatty-acyl-CoA and is active in membrane assembly. We have previously described the behavior of ACBP under tension, revealing a highly extended transition state (TS) located almost halfway between the unfolded and native states. Here, we performed force-ramp and force-jump experiments, in combination with advanced statistical analysis, to show that octanoyl-CoA binding increases the activation free energy for the unfolding reaction of ACBP without affecting the position of the transition state along the reaction coordinate. It follows that ligand binding enhances the mechanical resistance and thermodynamic stability of the protein, without changing its mechanical compliance. Steered molecular dynamics simulations allowed us to rationalize the results in terms of key interactions that octanoyl-CoA establishes with the four α-helices of ACBP and showed that the unfolding pathway is marginally affected by the ligand. The results show that ligand-induced mechanical stabilization effects can be complex and may prove useful for the rational design of stabilizing ligands.
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Affiliation(s)
- Punam Sonar
- Physik-Department E22, Technische Universität München, Garching Germany
| | - Luca Bellucci
- NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, Piazza San Silvestro 12, Pisa, Italy
| | - Alessandro Mossa
- INFN Firenze, Sesto Fiorentino, Italy; Istituto Statale di Istruzione Superiore "Leonardo da Vinci", Firenze, Italy.
| | - Pétur O Heidarsson
- Department of Biochemistry, Science Institute, University of Iceland, Reykjavík, Iceland.
| | - Birthe B Kragelund
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Copenhagen N, Denmark.
| | - Ciro Cecconi
- Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, Modena, Italy; Center S3, CNR Institute Nanoscience, Modena, Italy.
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5
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Munshi S, Rajendran D, Ramesh S, Subramanian S, Bhattacharjee K, Kumar MR, Naganathan AN. Controlling Structure and Dimensions of a Disordered Protein via Mutations. Biochemistry 2019; 59:171-174. [PMID: 31557007 PMCID: PMC7115935 DOI: 10.1021/acs.biochem.9b00678] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The dimensions of intrinsically disordered proteins (IDPs) are sensitive to small energetic-entropic differences between intramolecular and protein–solvent interactions. This is commonly observed on modulating solvent composition and temperature. However, the inherently heterogeneous conformational landscape of IDPs is also expected to be influenced by mutations that can (de)stabilize pockets of local and even global structure, native and non-native, and hence the average dimensions. Here, we show experimental evidence for the remarkably tunable landscape of IDPs by employing the DNA-binding domain of CytR, a high-sequence-complexity IDP, as a model system. CytR exhibits a range of structure and compactness upon introducing specific mutations that modulate microscopic terms, including main-chain entropy, hydrophobicity, and electrostatics. The degree of secondary structure, as monitored by far-UV circular dichroism (CD), is strongly correlated to average ensemble dimensions for 14 different mutants of CytR and is consistent with the Uversky–Fink relation. Our experiments highlight how average ensemble dimensions can be controlled via mutations even in the disordered regime, the prevalence of non-native interactions and provide testable controls for molecular simulations.
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Affiliation(s)
- Sneha Munshi
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| | - Divya Rajendran
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| | - Samyuktha Ramesh
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| | - Sandhyaa Subramanian
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| | - Kabita Bhattacharjee
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| | - Meagha Ramana Kumar
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
| | - Athi N Naganathan
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences , Indian Institute of Technology Madras , Chennai 600036 , India
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6
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Khor S. Folding with a protein's native shortcut network. Proteins 2019; 86:924-934. [PMID: 29790602 DOI: 10.1002/prot.25524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 04/13/2018] [Accepted: 05/14/2018] [Indexed: 11/09/2022]
Abstract
A complex network approach to protein folding is proposed, wherein a protein's contact map is reconceptualized as a network of shortcut edges, and folding is steered by a structural characteristic of this network. Shortcut networks are generated by a known message passing algorithm operating on protein residue networks. It is found that the shortcut networks of native structures (SCN0s) are relevant graph objects with which to study protein folding at a formal level. The logarithm form of their contact order (SCN0_lnCO) correlates significantly with folding rate of two-state and nontwo-state proteins. The clustering coefficient of SCN0s (CSCN0 ) correlates significantly with folding rate, transition-state placement and stability of two-state folders. Reasonable folding pathways for several model proteins are produced when CSCN0 is used to combine protein segments incrementally to form the native structure. The folding bias captured by CSCN0 is detectable in non-native structures, as evidenced by Molecular Dynamics simulation generated configurations for the fast folding Villin-headpiece peptide. These results support the use of shortcut networks to investigate the role protein geometry plays in the folding of both small and large globular proteins, and have implications for the design of multibody interaction schemes in folding models. One facet of this geometry is the set of native shortcut triangles, whose attributes are found to be well-suited to identify dehydrated intraprotein areas in tight turns, or at the interface of different secondary structure elements.
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Affiliation(s)
- Susan Khor
- Department of Computer Science, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
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7
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Thakur AK, Meng W, Gierasch LM. Local and non-local topological information in the denatured state ensemble of a β-barrel protein. Protein Sci 2018; 27:2062-2072. [PMID: 30252171 DOI: 10.1002/pro.3516] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 09/18/2018] [Accepted: 09/19/2018] [Indexed: 11/06/2022]
Abstract
The folding of predominantly β-sheet proteins is complicated by the presence of a large number of non-local interactions in their native states, which increase the ruggedness of their folding energy landscapes. However, forming non-local contacts early in folding or even in the unfolded state can smooth the energy landscape and facilitate productive folding. We report that several sequence regions of a β-barrel protein, cellular retinoic acid-binding protein 1 (CRABP1), populate native-like secondary structure to a significant extent in the denatured state in 8 M urea. In addition, we provide evidence for both local and non-local interactions in the denatured state of CRABP1. NMR chemical shift perturbations (CSPs) under denaturing conditions upon substitution of single residues by mutation support the presence of several non-local interactions in topologically key sites, arguing that the denatured state is conformationally restricted and contains topological information for the native fold. Among the most striking non-local interactions are those between the N- and C-terminal regions, which are involved in closure of the native β-barrel. In addition, CSPs support the presence of two features in the denatured state: a major hydrophobic cluster involving residues from various parts of the sequence and a native-like interaction similar to one identified in previous studies as forming early in folding (Budyak et al., Structure 21, 476 [2013]). Taken together, our data support a model in which transient structures involving nonlocal interactions prime early folding interactions in CRABP1, determine its barrel topology, and may protect this predominantly β-sheet protein against aggregation.
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Affiliation(s)
- Abhay K Thakur
- Departments of Biochemistry & Molecular Biology and Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts, 01003
| | - Wenli Meng
- Departments of Biochemistry & Molecular Biology and Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts, 01003
| | - Lila M Gierasch
- Departments of Biochemistry & Molecular Biology and Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts, 01003
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8
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Entropic Control of an Excited Folded-Like Conformation in a Disordered Protein Ensemble. J Mol Biol 2018; 430:2688-2694. [PMID: 29885328 PMCID: PMC6166778 DOI: 10.1016/j.jmb.2018.06.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 05/09/2018] [Accepted: 06/04/2018] [Indexed: 12/14/2022]
Abstract
Many intrinsically disordered proteins switch between unfolded and folded-like forms in the presence of their binding partner. The possibility of a pre-equilibrium between the two macrostates is challenging to discern given the complex conformational landscape. Here, we show that CytR, a disordered DNA-binding domain, samples a folded-like excited state in its native ensemble through equilibrium multi-probe spectroscopy, kinetics and an Ising-like statistical mechanical model. The population of the excited state increases upon stabilization of the native ensemble with an osmolyte, while decreasing with increasing temperatures. A conserved proline residue, the mutation of which weakens the binding affinity to the target promoter, is found to uniquely control the population of the minor excited state. Semi-quantitative statistical mechanical modeling reveals that the conformational diffusion coefficient of disordered CytR is an order of magnitude slower than the estimates from folded domains. The osmolyte and proline mutation smoothen and roughen up the landscape, respectively, apart from modulation of populations. Our work uncovers general strategies to probe for excited structured states in disordered ensembles, and to measure and modulate the roughness of the disordered landscapes, inter-conversion rates of species and their populations.
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9
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Leavens MJ, Cherney MM, Finnegan ML, Bowler BE. Probing Denatured State Conformational Bias in a Three-Helix Bundle, UBA(2), Using a Cytochrome c Fusion Protein. Biochemistry 2018; 57:1711-1721. [PMID: 29480716 DOI: 10.1021/acs.biochem.8b00015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Previous work with the four-helix-bundle protein cytochrome c' from Rhodopseudomonas palustris using histidine-heme loop formation methods revealed fold-specific deviations from random coil behavior in its denatured state ensemble. To examine the generality of this finding, we extend this work to a three-helix-bundle polypeptide, the second ubiquitin-associated domain, UBA(2), of the human DNA excision repair protein. We use yeast iso-1-cytochrome c as a scaffold, fusing the UBA(2) domain at the N-terminus of iso-1-cytochrome c. We have engineered histidine into highly solvent accessible positions of UBA(2), creating six single histidine variants. Guanidine hydrochloride denaturation studies show that the UBA(2)-cytochrome c fusion protein unfolds in a three-state process with iso-1-cytochrome c unfolding first. Furthermore, engineered histidine residues in UBA(2) strongly destabilize the iso-1-cytochrome c domain. Equilibrium and kinetic histidine-heme loop formation measurements in the denatured state at 4 and 6 M guanidine hydrochloride show that loop stability decreases as the size of the histidine-heme loop increases, in accord with the Jacobson-Stockmayer equation. However, we observe that the His27-heme loop is both more stable than expected from the Jacobson-Stockmayer relationship and breaks more slowly than expected. These results show that the sequence near His27, which is in the reverse turn between helices 2 and 3 of UBA(2), is prone to persistent interactions in the denatured state. Therefore, consistent with our results for cytochrome c', this reverse turn sequence may help to establish the topology of this fold by biasing the conformational distribution of the denatured state.
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Affiliation(s)
- Moses J Leavens
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Dynamics , University of Montana , Missoula , Montana 59812 , United States
| | - Melisa M Cherney
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Dynamics , University of Montana , Missoula , Montana 59812 , United States
| | - Michaela L Finnegan
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Dynamics , University of Montana , Missoula , Montana 59812 , United States
| | - Bruce E Bowler
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Dynamics , University of Montana , Missoula , Montana 59812 , United States
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10
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Danielson TA, Bowler BE. Helical Propensity Affects the Conformational Properties of the Denatured State of Cytochrome c'. Biophys J 2018; 114:311-322. [PMID: 29401429 DOI: 10.1016/j.bpj.2017.11.3744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 10/18/2017] [Accepted: 11/21/2017] [Indexed: 10/18/2022] Open
Abstract
Changing the helical propensity of a polypeptide sequence might be expected to affect the conformational properties of the denatured state of a protein. To test this hypothesis, alanines at positions 83 and 87 near the center of helix 3 of cytochrome c' from Rhodopseudomonas palustris were mutated to serine to decrease the stability of this helix. A set of 13 single histidine variants in the A83S/A87S background were prepared to permit assessment of the conformational properties of the denatured state using histidine-loop formation in 3 M guanidine hydrochloride. The data are compared with previous histidine-heme loop formation data for wild-type cytochrome c'. As expected, destabilization of helix 3 decreases the global stabilities of the histidine variants in the A83S/A87S background relative to the wild-type background. Loop stability versus loop size data yields a scaling exponent of 2.1 ± 0.2, similar to the value of 2.3 ± 0.2 obtained for wild-type cytochrome c'. However, the stabilities of all histidine-heme loops, which contain the helix 3 sequence segment, are increased in the A83S/A87S background compared to the wild-type background. Rate constants for histidine-heme loop breakage are similar for the wild-type and A83S/A87S variants. However, for histidine-heme loops that contain the helix 3 sequence segment, the rate constants for loop formation increase in the A83S/A87S background compared to the wild-type background. Thus, residual helical structure appears to stiffen the polypeptide chain slowing loop formation in the denatured state. The implications of these results for protein folding mechanisms are discussed.
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Affiliation(s)
- Travis A Danielson
- Department of Chemistry and Biochemistry and Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, Montana
| | - Bruce E Bowler
- Department of Chemistry and Biochemistry and Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, Montana.
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11
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Danielson TA, Stine JM, Dar TA, Briknarova K, Bowler BE. Effect of an Imposed Contact on Secondary Structure in the Denatured State of Yeast Iso-1-cytochrome c. Biochemistry 2017; 56:6662-6676. [PMID: 29148740 DOI: 10.1021/acs.biochem.7b01002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
There is considerable evidence that long-range interactions stabilize residual protein structure under denaturing conditions. However, evaluation of the effect of a specific contact on structure in the denatured state has been difficult. Iso-1-cytochrome c variants with a Lys54 → His mutation form a particularly stable His-heme loop in the denatured state, suggestive of loop-induced residual structure. We have used multidimensional nuclear magnetic resonance methods to assign 1H and 15N backbone amide and 13C backbone and side chain chemical shifts in the denatured state of iso-1-cytochrome c carrying the Lys54 → His mutation in 3 and 6 M guanidine hydrochloride and at both pH 6.4, where the His54-heme loop is formed, and pH 3.6, where the His54-heme loop is broken. Using the secondary structure propensity score, with the 6 M guanidine hydrochloride chemical shift data as a random coil reference state for data collected in 3 M guanidine hydrochloride, we found residual helical structure in the denatured state for the 60s helix and the C-terminal helix, but not in the N-terminal helix in the presence or absence of the His54-heme loop. Non-native helical structure is observed in two regions that form Ω-loops in the native state. There is more residual helical structure in the C-terminal helix at pH 6.4 when the loop is formed. Loop formation also appears to stabilize helical structure near His54, consistent with induction of helical structure observed when His-heme bonds form in heme-peptide model systems. The results are discussed in the context of the folding mechanism of cytochrome c.
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Affiliation(s)
- Travis A Danielson
- Department of Chemistry and Biochemistry, University of Montana , Missoula, Montana 59812, United States
| | - Jessica M Stine
- Department of Chemistry and Biochemistry, University of Montana , Missoula, Montana 59812, United States
| | - Tanveer A Dar
- Department of Chemistry and Biochemistry, University of Montana , Missoula, Montana 59812, United States
| | - Klara Briknarova
- Department of Chemistry and Biochemistry, University of Montana , Missoula, Montana 59812, United States.,Center for Biomolecular Structure and Dynamics, University of Montana , Missoula, Montana 59812, United States
| | - Bruce E Bowler
- Department of Chemistry and Biochemistry, University of Montana , Missoula, Montana 59812, United States.,Center for Biomolecular Structure and Dynamics, University of Montana , Missoula, Montana 59812, United States
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12
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Exploring the Denatured State Ensemble by Single-Molecule Chemo-Mechanical Unfolding: The Effect of Force, Temperature, and Urea. J Mol Biol 2017; 430:450-464. [PMID: 28782558 DOI: 10.1016/j.jmb.2017.07.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 07/29/2017] [Accepted: 07/31/2017] [Indexed: 11/22/2022]
Abstract
While it is widely appreciated that the denatured state of a protein is a heterogeneous conformational ensemble, there is still debate over how this ensemble changes with environmental conditions. Here, we use single-molecule chemo-mechanical unfolding, which combines force and urea using the optical tweezers, together with traditional protein unfolding studies to explore how perturbants commonly used to unfold proteins (urea, force, and temperature) affect the denatured-state ensemble. We compare the urea m-values, which report on the change in solvent accessible surface area for unfolding, to probe the denatured state as a function of force, temperature, and urea. We find that while the urea- and force-induced denatured states expose similar amounts of surface area, the denatured state at high temperature and low urea concentration is more compact. To disentangle these two effects, we use destabilizing mutations that shift the Tm and Cm. We find that the compaction of the denatured state is related to changing temperature as the different variants of acyl-coenzyme A binding protein have similar m-values when they are at the same temperature but different urea concentration. These results have important implications for protein folding and stability under different environmental conditions.
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13
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Williams MJ, Bachmann M. The effect of surface adsorption on tertiary structure formation in helical polymers. J Chem Phys 2017; 147:024902. [DOI: 10.1063/1.4991564] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Matthew J. Williams
- Institute of Engineering, Murray State University, Murray, Kentucky 42071, USA
- Soft Matter Systems Research Group, Center for Simulational Physics, The University of Georgia, Athens, Georgia 30602, USA
| | - Michael Bachmann
- Soft Matter Systems Research Group, Center for Simulational Physics, The University of Georgia, Athens, Georgia 30602, USA
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14
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Micheletto MC, Mendes LFS, Basso LGM, Fonseca-Maldonado RG, Costa-Filho AJ. Lipid membranes and acyl-CoA esters promote opposing effects on acyl-CoA binding protein structure and stability. Int J Biol Macromol 2017; 102:284-296. [PMID: 28390829 DOI: 10.1016/j.ijbiomac.2017.03.197] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 03/23/2017] [Accepted: 03/27/2017] [Indexed: 12/21/2022]
Abstract
Acyl-CoA Binding Proteins (ACBP) form a housekeeping family of proteins that is responsible for the buffering of long chain acyl-coenzyme A esters (LCFA-CoA) inside the cell. Even though numerous studies have focused on the characterization of different members of the ACBP family, the knowledge about the impact of both LCFA-CoA and phospholipids on ACBP structure and stability remains scarce. Besides, there are still controversies regarding the possible interaction of ACBP with biological membranes, even though this might be essential for the cargo capture and delivery. In this study, we observed that LCFA-CoA and phospholipids play opposite roles on protein stability and that the interaction with the membrane is dictated by electrostatic interaction. Furthermore, the results support the hypothesis that the LCFA-CoA delivery is driven by the increase of the negative charge on the membrane surface. The combined influence played by the different molecules on ACBP structure is discussed on the light of cargo capture/delivery giving new insights about this important process.
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Affiliation(s)
- Mariana C Micheletto
- Laboratório de Biofísica Molecular, Departamento de Física, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Luís F S Mendes
- Laboratório de Biofísica Molecular, Departamento de Física, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Luis G M Basso
- Laboratório de Biofísica Molecular, Departamento de Física, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Raquel G Fonseca-Maldonado
- Laboratório de Biofísica Molecular, Departamento de Física, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil; Instituto Federal de Educação, Ciência e Tecnologia de São Paulo/IFSP Campus Jacareí-Dept Gestão, Brazil
| | - Antonio J Costa-Filho
- Laboratório de Biofísica Molecular, Departamento de Física, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
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15
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Jeong WJ, Choi SH, Jin KS, Lim YB. Tuning Oligovalent Biomacromolecular Interfaces Using Double-Layered α-Helical Coiled-Coil Nanoassemblies from Lariat-Type Building Blocks. ACS Macro Lett 2016; 5:1406-1410. [PMID: 35651205 DOI: 10.1021/acsmacrolett.6b00746] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The target affinity and selectivity of many biomacromolecules depend on the three-dimensional (3D) distribution of multiple ligands on their surfaces. Here, we devised a self-assembly strategy to control the target-tailored 3D distribution of multiple α-helical ligands on a coiled-coil core scaffold using novel lariat-type supramolecular building blocks. Depending on the coiled-coil composition and ligand grafting sites in the lariat building blocks, the structural and functional features of the self-assembled peptide nanostructures (SPNs) could be variably fine-tuned. Using oligovalent protein-RNA (Rev-RRE) interactions as a model system, we demonstrate that longer grafting reinforces the helicity of the peptide ligands, whereas shorter grafting strengthens the target binding affinity of the SPNs in both monovalent and oligovalent interactions. This supramolecular approach should be useful in developing precisely controllable multivalent ligands for biomacromolecular interactions.
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Affiliation(s)
- Woo-jin Jeong
- Department of Materials Science & Engineering, Yonsei University, Seoul 120-749, Korea
| | - Se-Hwan Choi
- Department of Materials Science & Engineering, Yonsei University, Seoul 120-749, Korea
| | - Kyeong Sik Jin
- Pohang
Accelerator Laboratory, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Yong-beom Lim
- Department of Materials Science & Engineering, Yonsei University, Seoul 120-749, Korea
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16
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De Mol E, Fenwick RB, Phang CTW, Buzón V, Szulc E, de la Fuente A, Escobedo A, García J, Bertoncini CW, Estébanez-Perpiñá E, McEwan IJ, Riera A, Salvatella X. EPI-001, A Compound Active against Castration-Resistant Prostate Cancer, Targets Transactivation Unit 5 of the Androgen Receptor. ACS Chem Biol 2016; 11:2499-505. [PMID: 27356095 DOI: 10.1021/acschembio.6b00182] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Castration-resistant prostate cancer is the lethal condition suffered by prostate cancer patients that become refractory to androgen deprivation therapy. EPI-001 is a recently identified compound active against this condition that modulates the activity of the androgen receptor, a nuclear receptor that is essential for disease progression. The mechanism by which this compound exerts its inhibitory activity is however not yet fully understood. Here we show, by using high resolution solution nuclear magnetic resonance spectroscopy, that EPI-001 selectively interacts with a partially folded region of the transactivation domain of the androgen receptor, known as transactivation unit 5, that is key for the ability of prostate cells to proliferate in the absence of androgens, a distinctive feature of castration-resistant prostate cancer. Our results can contribute to the development of more potent and less toxic novel androgen receptor antagonists for treating this disease.
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Affiliation(s)
- Eva De Mol
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain
| | - R. Bryn Fenwick
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain
| | - Christopher T. W. Phang
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain
| | - Victor Buzón
- Departament
de Bioquímica i Biología Molecular, and Institute of
Biomedicine, University of Barcelona (IBUB), Baldiri Reixac 10, 08028 Barcelona, Spain
| | - Elzbieta Szulc
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain
| | - Alex de la Fuente
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain
| | - Albert Escobedo
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain
| | - Jesús García
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain
| | - Carlos W. Bertoncini
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain
| | - Eva Estébanez-Perpiñá
- Departament
de Bioquímica i Biología Molecular, and Institute of
Biomedicine, University of Barcelona (IBUB), Baldiri Reixac 10, 08028 Barcelona, Spain
| | - Iain J. McEwan
- Institute
of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, IMS Building, Foresterhill, Aberdeen AB25 2ZD, Scotland, United Kingdom
| | - Antoni Riera
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain
- Departament
de Química Orgànica, Universitat de Barcelona, Martí
i Franqués 1-11, 08028 Barcelona, Spain
| | - Xavier Salvatella
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain
- ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain
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17
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Zhan Y, Giorgetti L, Tiana G. Looping probability of random heteropolymers helps to understand the scaling properties of biopolymers. Phys Rev E 2016; 94:032402. [PMID: 27739813 DOI: 10.1103/physreve.94.032402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Indexed: 06/06/2023]
Abstract
Random heteropolymers are a minimal description of biopolymers and can provide a theoretical framework to the investigate the formation of loops in biophysical experiments. The looping probability as a function of polymer length was observed to display in some biopolymers, like chromosomes in cell nuclei or long RNA chains, anomalous scaling exponents. Combining a two-state model with self-adjusting simulated-tempering calculations, we calculate numerically the looping properties of several realizations of the random interactions within the chain. We find a continuous set of exponents upon varying the temperature, which arises from finite-size effects and is amplified by the disorder of the interactions. We suggest that this could provide a simple explanation for the anomalous scaling exponents found in experiments. In addition, our results have important implications notably for the study of chromosome folding as they show that scaling exponents cannot be the sole criteria for testing hypothesis-driven models of chromosome architecture.
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Affiliation(s)
- Y Zhan
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
| | - L Giorgetti
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
| | - G Tiana
- Center for Complexity and Biosystems and Department of Physics, Università degli Studi di Milano and INFN, via Celoria 16, 20133 Milano, Italy
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18
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Williams MJ, Bachmann M. System-Size Dependence of Helix-Bundle Formation for Generic Semiflexible Polymers. Polymers (Basel) 2016; 8:E245. [PMID: 30974521 PMCID: PMC6431926 DOI: 10.3390/polym8070245] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 06/20/2016] [Accepted: 06/20/2016] [Indexed: 11/16/2022] Open
Abstract
Helical polymer bundles are an important fixture in biomolecular systems. The particular structural geometry of helix bundles is dependent on many factors including the length of the polymer chain. In this study, we performed Monte Carlo simulations of a coarse-grained model for helical polymers to determine the influence of polymer length on tertiary structure formation. Helical structures of semiflexible polymers are analyzed for several chain lengths under thermal conditions. Structural hyperphase diagrams, parametrized by torsion strength and temperature, are constructed and compared.
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Affiliation(s)
- Matthew J Williams
- Soft Matter Systems Research Group, Center for Simulational Physics, The University of Georgia, Athens, GA 30602, USA.
| | - Michael Bachmann
- Soft Matter Systems Research Group, Center for Simulational Physics, The University of Georgia, Athens, GA 30602, USA.
- Instituto de Física, Universidade Federal de Mato Grosso, 78060-900 Cuiabá (MT), Brazil.
- Departamento de Física, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte (MG), Brazil.
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19
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Williams MJ, Bachmann M. Significance of bending restraints for the stability of helical polymer conformations. Phys Rev E 2016; 93:062501. [PMID: 27415311 DOI: 10.1103/physreve.93.062501] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Indexed: 01/30/2023]
Abstract
We performed parallel-tempering Monte Carlo simulations to investigate the formation and stability of helical tertiary structures for flexible and semiflexible polymers, employing a generic coarse-grained model. Structural conformations exhibit helical order with tertiary ordering into single helices, multiple helical segments organized into bundles, and disorganized helical arrangements. For both bending-restrained semiflexible and bending-unrestrained flexible helical polymers, the stability of the structural phases is discussed systematically by means of hyperphase diagrams parametrized by suitable order parameters, temperature, and torsion strength. This exploration lends insight into the restricted flexibility of biological polymers such as double-stranded DNA and proteins.
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Affiliation(s)
- Matthew J Williams
- Soft Matter Systems Research Group, Center for Simulational Physics, The University of Georgia, Athens, Georgia 30602, USA
| | - Michael Bachmann
- Soft Matter Systems Research Group, Center for Simulational Physics, The University of Georgia, Athens, Georgia 30602, USA.,Instituto de Física, Universidade Federal de Mato Grosso, Cuiabá (MT), Brazil.,Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte (MG), Brazil
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20
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Chen W, Shi C, Shen J. Nascent β-Hairpin Formation of a Natively Unfolded Peptide Reveals the Role of Hydrophobic Contacts. Biophys J 2016; 109:630-8. [PMID: 26244744 PMCID: PMC4571001 DOI: 10.1016/j.bpj.2015.06.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 06/16/2015] [Accepted: 06/17/2015] [Indexed: 11/21/2022] Open
Abstract
Despite the important role of the unfolded states in protein stability, folding, and aggregation, they remain poorly understood due to the lack of residue-specific experimental data. Here, we explore features of the unfolded state of the NTL9 protein by applying all-atom replica-exchange simulations to the two fragment peptides NTL9(1–22) and NTL9(6–17). We found that while NTL9(6–17) is unstructured, NTL9(1–22) transiently folds as various β-hairpins, a fraction of which contain a native β-sheet. Interestingly, despite a large number of charged residues, the formation of backbone hydrogen bonds is concomitant with hydrophobic but not electrostatic contacts. Although the fragment peptides lack a proposed specific contact between Asp8 and Lys12, the individually weak, nonspecific interactions with lysines together stabilize the charged Asp8, leading to a pKa shift of nearly 0.5 units, in agreement with the NMR data. Taken together, our data suggest that the unfolded state of NTL9 likely contains a β-hairpin in segment 1–22 with sequence-distant hydrophobic contacts, thus lending support to a long-standing hypothesis that the unfolded states of proteins exhibit native-like topology with hydrophobic clusters.
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Affiliation(s)
- Wei Chen
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland
| | - Chuanyin Shi
- Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai, China
| | - Jana Shen
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland.
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21
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Munshi S, Naganathan AN. Imprints of function on the folding landscape: functional role for an intermediate in a conserved eukaryotic binding protein. Phys Chem Chem Phys 2016; 17:11042-52. [PMID: 25824585 DOI: 10.1039/c4cp06102k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In the computational characterization of single domain protein folding, the effective free energies of numerous microstates are projected onto few collective degrees of freedom that in turn serve as well-defined reaction coordinates. In this regard, one-dimensional (1D) free energy profiles are widely used mainly for their simplicity. Since folding and functional landscapes are interlinked, how well can these reduced representations capture the structural and dynamic features of functional states while being simultaneously consistent with experimental observables? We investigate this issue by characterizing the folding of the four-helix bundle bovine acyl-CoA binding protein (bACBP), which exhibits complex equilibrium and kinetic behaviours, employing an Ising-like statistical mechanical model and molecular simulations. We show that the features of the 1D free energy profile are sufficient to quantitatively reproduce multiple experimental observations including millisecond chevron-like kinetics and temperature dependence, a microsecond fast phase, barrier heights, unfolded state movements, the intermediate structure and average ϕ-values. Importantly, we find that the structural features of the native-like intermediate (partial disorder in helix 1) are intricately linked to a unique interplay between packing and electrostatics in this domain. By comparison with available experimental data, we propose that this intermediate determines the promiscuous functional behaviour of bACBP that exhibits broad substrate specificity. Our results present evidence to the possibility of employing the statistical mechanical model and the resulting 1D free energy profile to not just understand folding mechanisms but to even extract features of functionally relevant states and their energetic origins.
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Affiliation(s)
- Sneha Munshi
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600036, India.
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22
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Williams MJ, Bachmann M. Stabilization of Helical Macromolecular Phases by Confined Bending. PHYSICAL REVIEW LETTERS 2015; 115:048301. [PMID: 26252710 DOI: 10.1103/physrevlett.115.048301] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Indexed: 06/04/2023]
Abstract
By means of extensive replica-exchange simulations of generic coarse-grained models for helical polymers, we systematically investigate the structural transitions into all possible helical phases for flexible and semiflexible elastic polymers with self-interaction under the influence of torsion barriers. The competing interactions lead to a variety of conformational phases including disordered helical arrangements, single helices, and ordered, tertiary helix bundles. Most remarkably, we find that a bending restraint entails a clear separation and stabilization of the helical phases. This aids in understanding why semiflexible polymers such as double-stranded DNA tend to form pronounced helical structures and proteins often exhibit an abundance of helical structures, such as helix bundles, within their tertiary structure.
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Affiliation(s)
- Matthew J Williams
- Soft Matter Systems Research Group, Center for Simulational Physics, The University of Georgia, Athens, Georgia 30602, USA
| | - Michael Bachmann
- Soft Matter Systems Research Group, Center for Simulational Physics, The University of Georgia, Athens, Georgia 30602, USA
- Instituto de Física, Universidade Federal de Mato Grosso, 78060-900 Cuiabá (MT), Brazil
- Departamento de Física, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte (MG), Brazil
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23
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Tiana G. Effect of disorder on the contact probability of elongated conformations of biopolymers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:010702. [PMID: 26274109 DOI: 10.1103/physreve.92.010702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Indexed: 06/04/2023]
Abstract
Biopolymers are characterized by heterogeneous interactions, and usually perform their biological tasks forming contacts within domains of limited size. Combining polymer theory with a replica approach, we study the scaling properties of the probability of contact formation in random heteropolymers as a function of their linear distance. It is found that, close to or above the θ point, it is possible to define a contact probability which is typical (i.e., "self-averaging") for different realizations of the heterogeneous interactions, and which displays an exponential cutoff, dependent on temperature and on the interaction range. In many cases this cutoff is comparable with the typical sizes of domains in biopolymers. While it is well known that disorder causes interesting effects at low temperature, the behavior elucidated in the present study is an example of a nontrivial effect at high temperature.
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Affiliation(s)
- Guido Tiana
- Department of Physics, Università degli Studi di Milano and INFN, via Celoria 16, 20133 Milano, Italy
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24
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Mantsyzov AB, Maltsev AS, Ying J, Shen Y, Hummer G, Bax A. A maximum entropy approach to the study of residue-specific backbone angle distributions in α-synuclein, an intrinsically disordered protein. Protein Sci 2014; 23:1275-90. [PMID: 24976112 DOI: 10.1002/pro.2511] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 06/16/2014] [Indexed: 01/16/2023]
Abstract
α-Synuclein is an intrinsically disordered protein of 140 residues that switches to an α-helical conformation upon binding phospholipid membranes. We characterize its residue-specific backbone structure in free solution with a novel maximum entropy procedure that integrates an extensive set of NMR data. These data include intraresidue and sequential H(N) − H(α) and H(N) − H(N) NOEs, values for (3) JHNHα, (1) JHαCα, (2) JCαN, and (1) JCαN, as well as chemical shifts of (15)N, (13)C(α), and (13)C' nuclei, which are sensitive to backbone torsion angles. Distributions of these torsion angles were identified that yield best agreement to the experimental data, while using an entropy term to minimize the deviation from statistical distributions seen in a large protein coil library. Results indicate that although at the individual residue level considerable deviations from the coil library distribution are seen, on average the fitted distributions agree fairly well with this library, yielding a moderate population (20-30%) of the PPII region and a somewhat higher population of the potentially aggregation-prone β region (20-40%) than seen in the database. A generally lower population of the αR region (10-20%) is found. Analysis of (1)H − (1)H NOE data required consideration of the considerable backbone diffusion anisotropy of a disordered protein.
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Affiliation(s)
- Alexey B Mantsyzov
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, 20892
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25
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Camilloni C, Vendruscolo M. Statistical mechanics of the denatured state of a protein using replica-averaged metadynamics. J Am Chem Soc 2014; 136:8982-91. [PMID: 24884637 DOI: 10.1021/ja5027584] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The characterization of denatured states of proteins is challenging because the lack of permanent structure in these states makes it difficult to apply to them standard methods of structural biology. In this work we use all-atom replica-averaged metadynamics (RAM) simulations with NMR chemical shift restraints to determine an ensemble of structures representing an acid-denatured state of the 86-residue protein ACBP. This approach has enabled us to reach convergence in the free energy landscape calculations, obtaining an ensemble of structures in relatively accurate agreement with independent experimental data used for validation. By observing at atomistic resolution the transient formation of native and non-native structures in this acid-denatured state of ACBP, we rationalize the effects of single-point mutations on the folding rate, stability, and transition-state structures of this protein, thus characterizing the role of the unfolded state in determining the folding process.
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Affiliation(s)
- Carlo Camilloni
- Department of Chemistry, University of Cambridge , Cambridge CB2 1EW, United Kingdom
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26
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Transient α-helices in the disordered RPEL motifs of the serum response factor coactivator MKL1. Sci Rep 2014; 4:5224. [PMID: 24909411 PMCID: PMC4048911 DOI: 10.1038/srep05224] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 05/21/2014] [Indexed: 12/17/2022] Open
Abstract
The megakaryoblastic leukemia 1 (MKL1) protein functions as a transcriptional coactivator of the serum response factor. MKL1 has three RPEL motifs (RPEL1, RPEL2, and RPEL3) in its N-terminal region. MKL1 binds to monomeric G-actin through RPEL motifs, and the dissociation of MKL1 from G-actin promotes the translocation of MKL1 to the nucleus. Although structural data are available for RPEL motifs of MKL1 in complex with G-actin, the structural characteristics of RPEL motifs in the free state have been poorly defined. Here we characterized the structures of free RPEL motifs using NMR and CD spectroscopy. NMR and CD measurements showed that free RPEL motifs are largely unstructured in solution. However, NMR analysis identified transient α-helices in the regions where helices α1 and α2 are induced upon binding to G-actin. Proline mutagenesis showed that the transient α-helices are locally formed without helix-helix interactions. The helix content is higher in the order of RPEL1, RPEL2, and RPEL3. The amount of preformed structure may correlate with the binding affinity between the intrinsically disordered protein and its target molecule.
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27
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Exploring the Minimally Frustrated Energy Landscape of Unfolded ACBP. J Mol Biol 2014; 426:722-34. [DOI: 10.1016/j.jmb.2013.10.031] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 10/23/2013] [Accepted: 10/24/2013] [Indexed: 12/18/2022]
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28
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Iešmantavičius V, Jensen MR, Ozenne V, Blackledge M, Poulsen FM, Kjaergaard M. Modulation of the Intrinsic Helix Propensity of an Intrinsically Disordered Protein Reveals Long-Range Helix–Helix Interactions. J Am Chem Soc 2013; 135:10155-63. [DOI: 10.1021/ja4045532] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
| | - Malene Ringkjøbing Jensen
- Institut de Biologie Structurale Jean-Pierre Ebel, CEA-CNRS-UJF UMR 5075,
41 rue Jules Horowitz, 38027 Grenoble, France
| | - Valéry Ozenne
- Institut de Biologie Structurale Jean-Pierre Ebel, CEA-CNRS-UJF UMR 5075,
41 rue Jules Horowitz, 38027 Grenoble, France
| | - Martin Blackledge
- Institut de Biologie Structurale Jean-Pierre Ebel, CEA-CNRS-UJF UMR 5075,
41 rue Jules Horowitz, 38027 Grenoble, France
| | - Flemming M. Poulsen
- Department
of Biology, University of Copenhagen, 1017
København K, Copenhagen,
Denmark
| | - Magnus Kjaergaard
- Department
of Biology, University of Copenhagen, 1017
København K, Copenhagen,
Denmark
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29
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Shukla RT, Baliga C, Sasidhar YU. The role of loop closure propensity in the refolding of Rop protein probed by molecular dynamics simulations. J Mol Graph Model 2013; 40:10-21. [PMID: 23340205 DOI: 10.1016/j.jmgm.2012.12.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 12/26/2012] [Accepted: 12/27/2012] [Indexed: 11/17/2022]
Abstract
Rop protein is a homo-dimer of helix-turn-helix and has relatively slow folding and unfolding rates compared to other dimeric proteins of similar size. Fluorescence studies cited in literature suggest that mutation of turn residues D30-A31 to G30-G31 (Gly₂) increases its folding and unfolding rates considerably. A further increase in number of glycines in the turn region results in decrease of folding rates compared to Gly₂ mutant. To understand the effect of glycine mutation on folding/unfolding rates of Rop and the conformational nature of turn region involved in formation of early folding species, we performed molecular dynamics simulations of turn peptides, ²⁵KLNELDADEQ³⁴ (DA peptide), ²⁵KLNELGGDEQ³⁴ (G₂ peptide), ²⁵KLNELGGGDEQ³⁵ (G₃ peptide) and ²⁵KLNELGGGEQ³⁴ (G₃(') peptide) from Rop at 300 K. Further Wt-Rop and mutant G₂-Rop monomers and dimers were also studied separately by molecular dynamics simulations. Our results show that glycine based peptides (G(n) peptides) have a higher loop closure propensity compared to DA. Comparison of monomeric and dimeric Rop simulations suggests that dimeric Rop necessarily requires α(L) conformation to be sampled at D30/G30 position in the turn region. Since glycine (at position 30) can readily adopt α(L) conformation, G(n) loop plays a dual role in both facilitating loop closure as well as facilitating reorganization/packing of helices required for structural adjustment during dimer formation in the folding of Rop. Based on our simulation results and available literature, we suggest a tentative kinetic model for Rop folding which allows us to estimate the contribution of loop closure propensity to the overall folding rates.
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Affiliation(s)
- Rashmi Tambe Shukla
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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30
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Heidarsson PO, Naqvi MM, Sonar P, Valpapuram I, Cecconi C. Conformational Dynamics of Single Protein Molecules Studied by Direct Mechanical Manipulation. DYNAMICS OF PROTEINS AND NUCLEIC ACIDS 2013; 92:93-133. [DOI: 10.1016/b978-0-12-411636-8.00003-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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31
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Heidarsson PO, Valpapuram I, Camilloni C, Imparato A, Tiana G, Poulsen FM, Kragelund BB, Cecconi C. A Highly Compliant Protein Native State with a Spontaneous-like Mechanical Unfolding Pathway. J Am Chem Soc 2012; 134:17068-75. [DOI: 10.1021/ja305862m] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Pétur O. Heidarsson
- Structural Biology and NMR Laboratory,
Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen N, Denmark
| | - Immanuel Valpapuram
- Department of Physics, University of Modena and Reggio Emilia, Via Guiseppe
Campi, 41125 Modena, Italy
| | - Carlo Camilloni
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge
CB2 1EW, United Kingdom
| | - Alberto Imparato
- Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, Building 1520,
8000 Aarhus C, Denmark
| | - Guido Tiana
- Department
of Physics, University of Milano and INFN, Via Celoria 13, 20133
Milano, Italy
| | - Flemming M. Poulsen
- Structural Biology and NMR Laboratory,
Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen N, Denmark
| | - Birthe B. Kragelund
- Structural Biology and NMR Laboratory,
Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen N, Denmark
| | - Ciro Cecconi
- CNR-Nano,
Department of Physics, University of Modena and Reggio Emilia, Via Guiseppe
Campi, 41125 Modena, Italy
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32
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Voelz VA, Jäger M, Yao S, Chen Y, Zhu L, Waldauer SA, Bowman GR, Friedrichs M, Bakajin O, Lapidus LJ, Weiss S, Pande VS. Slow unfolded-state structuring in Acyl-CoA binding protein folding revealed by simulation and experiment. J Am Chem Soc 2012; 134:12565-77. [PMID: 22747188 DOI: 10.1021/ja302528z] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Protein folding is a fundamental process in biology, key to understanding many human diseases. Experimentally, proteins often appear to fold via simple two- or three-state mechanisms involving mainly native-state interactions, yet recent network models built from atomistic simulations of small proteins suggest the existence of many possible metastable states and folding pathways. We reconcile these two pictures in a combined experimental and simulation study of acyl-coenzyme A binding protein (ACBP), a two-state folder (folding time ~10 ms) exhibiting residual unfolded-state structure, and a putative early folding intermediate. Using single-molecule FRET in conjunction with side-chain mutagenesis, we first demonstrate that the denatured state of ACBP at near-zero denaturant is unusually compact and enriched in long-range structure that can be perturbed by discrete hydrophobic core mutations. We then employ ultrafast laminar-flow mixing experiments to study the folding kinetics of ACBP on the microsecond time scale. These studies, along with Trp-Cys quenching measurements of unfolded-state dynamics, suggest that unfolded-state structure forms on a surprisingly slow (~100 μs) time scale, and that sequence mutations strikingly perturb both time-resolved and equilibrium smFRET measurements in a similar way. A Markov state model (MSM) of the ACBP folding reaction, constructed from over 30 ms of molecular dynamics trajectory data, predicts a complex network of metastable stables, residual unfolded-state structure, and kinetics consistent with experiment but no well-defined intermediate preceding the main folding barrier. Taken together, these experimental and simulation results suggest that the previously characterized fast kinetic phase is not due to formation of a barrier-limited intermediate but rather to a more heterogeneous and slow acquisition of unfolded-state structure.
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Affiliation(s)
- Vincent A Voelz
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States
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33
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Khan MKA, Miller AL, Bowler BE. Tryptophan stabilizes His-heme loops in the denatured state only when it is near a loop end. Biochemistry 2012; 51:3586-95. [PMID: 22486179 DOI: 10.1021/bi300212a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We use a host-guest approach to evaluate the effect of Trp guest residues relative to Ala on the kinetics and thermodynamics of formation of His-heme loops in the denatured state of iso-1-cytochrome c at 1.5, 3.0, and 6.0 M guanidine hydrochloride (GdnHCl). Trp guest residues are inserted into an alanine-rich segment placed after a unique His near the N-terminus of iso-1-cytochrome c. Trp guest residues are either 4 or 10 residues from the His end of the 28-residue loop. We find the guest Trp stabilizes the His-heme loop at all GdnHCl concentrations when it is the 4th, but not the 10th, residue from the His end of the loop. Thus, residues near loop ends are most important in developing topological constraints in the denatured state that affect protein folding. In 1.5 M GdnHCl, the loop stabilization is ~0.7 kcal/mol, providing a thermodynamic rationale for the observation that Trp often mediates residual structure in the denatured state. Measurement of loop breakage rate constants, k(b,His), indicates that loop stabilization by the Trp guest residues occurs completely after the transition state for loop formation in 6.0 M GdnHCl. Under poorer solvent conditions, approximately half of the stabilization of the loop develops in the transition state, consistent with contacts in the denatured state being energetically downhill and providing evidence for funneling even near the rim of the folding funnel.
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Affiliation(s)
- Md Khurshid A Khan
- Department of Chemistry and Biochemistry, Biochemistry Program, and Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, Montana 59812, United States
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34
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Understanding how small helical proteins fold: conformational dynamics of Im proteins relevant to their folding landscapes. Biochem Soc Trans 2012; 40:424-8. [DOI: 10.1042/bst20110739] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Understanding the mechanism of folding of small proteins requires characterization of their starting unfolded states and any partially unfolded states populated during folding. Here, we review what is known from NMR about these states of Im7, a 4-helix bundle protein that folds via an on-pathway intermediate, and show that there is an alignment of non-native structure in urea-unfolded Im7 with the helices of native Im7 that is a consequence of hydrophobic helix-promoting residues also promoting cluster-formation in the unfolded protein. We suggest that this kind of alignment is present in other proteins and is relevant to how native state topology determines folding rates.
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35
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Kjaergaard M, Iešmantavičius V, Poulsen FM. The interplay between transient α-helix formation and side chain rotamer distributions in disordered proteins probed by methyl chemical shifts. Protein Sci 2012; 20:2023-34. [PMID: 21898648 DOI: 10.1002/pro.726] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The peptide backbones of disordered proteins are routinely characterized by NMR with respect to transient structure and dynamics. Little experimental information is, however, available about the side chain conformations and how structure in the backbone affects the side chains. Methyl chemical shifts can in principle report the conformations of aliphatic side chains in disordered proteins and in order to examine this two model systems were chosen: the acid denatured state of acyl-CoA binding protein (ACBP) and the intrinsically disordered activation domain of the activator for thyroid hormone and retinoid receptors (ACTR). We find that small differences in the methyl carbon chemical shifts due to the γ-gauche effect may provide information about the side chain rotamer distributions. However, the effects of neighboring residues on the methyl group chemical shifts obscure the direct observation of γ-gauche effect. To overcome this, we reference the chemical shifts to those in a more disordered state resulting in residue specific random coil chemical shifts. The (13)C secondary chemical shifts of the methyl groups of valine, leucine, and isoleucine show sequence specific effects, which allow a quantitative analysis of the ensemble of χ(2)-angles of especially leucine residues in disordered proteins. The changes in the rotamer distributions upon denaturation correlate to the changes upon helix induction by the co-solvent trifluoroethanol, suggesting that the side chain conformers are directly or indirectly related to formation of transient α-helices.
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Affiliation(s)
- Magnus Kjaergaard
- Department of Biology, University of Copenhagen, København N, Denmark
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36
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Pashley CL, Morgan GJ, Kalverda AP, Thompson GS, Kleanthous C, Radford SE. Conformational properties of the unfolded state of Im7 in nondenaturing conditions. J Mol Biol 2012; 416:300-18. [PMID: 22226836 PMCID: PMC3314952 DOI: 10.1016/j.jmb.2011.12.041] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 12/19/2011] [Accepted: 12/20/2011] [Indexed: 11/04/2022]
Abstract
The unfolded ensemble in aqueous solution represents the starting point of protein folding. Characterisation of this species is often difficult since the native state is usually predominantly populated at equilibrium. Previous work has shown that the four-helix protein, Im7 (immunity protein 7), folds via an on-pathway intermediate. While the transition states and folding intermediate have been characterised in atomistic detail, knowledge of the unfolded ensemble under the same ambient conditions remained sparse. Here, we introduce destabilising amino acid substitutions into the sequence of Im7, such that the unfolded state becomes predominantly populated at equilibrium in the absence of denaturant. Using far- and near-UV CD, fluorescence, urea titration and heteronuclear NMR experiments, we show that three amino acid substitutions (L18A-L19A-L37A) are sufficient to prevent Im7 folding, such that the unfolded state is predominantly populated at equilibrium. Using measurement of chemical shifts, (15)N transverse relaxation rates and sedimentation coefficients, we show that the unfolded species of L18A-L19A-L37A deviates significantly from random-coil behaviour. Specifically, we demonstrate that this unfolded species is compact (R(h)=25 Å) relative to the urea-denatured state (R(h)≥30 Å) and contains local clusters of hydrophobic residues in regions that correspond to the four helices in the native state. Despite these interactions, there is no evidence for long-range stabilising tertiary interactions or persistent helical structure. The results reveal an unfolded ensemble that is conformationally restricted in regions of the polypeptide chain that ultimately form helices I, II and IV in the native state.
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Key Words
- ts1, transition state 1
- ts2, transition state 2
- cole7, colicin e7
- ssp, secondary structure propensity
- smfret, single-molecule förster resonance energy transfer
- im7, immunity protein 7
- edta, ethylenediaminetetraacetic acid
- hsqc, heteronuclear single quantum coherence
- auc, analytical ultracentrifugation
- itc, isothermal titration calorimetry
- bmrb, biological magnetic resonance data bank
- noe, nuclear overhauser enhancement
- aabuf, average area buried upon folding
- pdb, protein data bank
- protein folding
- nmr
- unfolded ensemble
- denatured state
- immunity protein
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Affiliation(s)
- Clare L. Pashley
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Gareth J. Morgan
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Arnout P. Kalverda
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Gary S. Thompson
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | | | - Sheena E. Radford
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
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37
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Lindorff-Larsen K, Trbovic N, Maragakis P, Piana S, Shaw DE. Structure and dynamics of an unfolded protein examined by molecular dynamics simulation. J Am Chem Soc 2012; 134:3787-91. [PMID: 22339051 DOI: 10.1021/ja209931w] [Citation(s) in RCA: 189] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The accurate characterization of the structure and dynamics of proteins in disordered states is a difficult problem at the frontier of structural biology whose solution promises to further our understanding of protein folding and intrinsically disordered proteins. Molecular dynamics (MD) simulations have added considerably to our understanding of folded proteins, but the accuracy with which the force fields used in such simulations can describe disordered proteins is unclear. In this work, using a modern force field, we performed a 200 μs unrestrained MD simulation of the acid-unfolded state of an experimentally well-characterized protein, ACBP, to explore the extent to which state-of-the-art simulation can describe the structural and dynamical features of a disordered protein. By comparing the simulation results with the results of NMR experiments, we demonstrate that the simulation successfully captures important aspects of both the local and global structure. Our simulation was ~2 orders of magnitude longer than those in previous studies of unfolded proteins, a length sufficient to observe repeated formation and breaking of helical structure, which we found to occur on a multimicrosecond time scale. We observed one structural feature that formed but did not break during the simulation, highlighting the difficulty in sampling disordered states. Overall, however, our simulation results are in reasonable agreement with the experimental data, demonstrating that MD simulations can already be useful in describing disordered proteins. Finally, our direct calculation of certain NMR observables from the simulation provides new insight into the general relationship between structural features of disordered proteins and experimental NMR relaxation properties.
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38
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Kjaergaard M, Poulsen FM. Disordered proteins studied by chemical shifts. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2012; 60:42-51. [PMID: 22293398 DOI: 10.1016/j.pnmrs.2011.10.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Accepted: 10/06/2011] [Indexed: 05/31/2023]
Affiliation(s)
- Magnus Kjaergaard
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 København N, Denmark
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39
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Bowler BE. Residual structure in unfolded proteins. Curr Opin Struct Biol 2011; 22:4-13. [PMID: 21978577 DOI: 10.1016/j.sbi.2011.09.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 09/07/2011] [Indexed: 11/27/2022]
Abstract
The denatured state ensemble (DSE) of unfolded proteins, once considered to be well-modeled by an energetically featureless random coil, is now well-known to contain flickering elements of residual structure. The position and nature of DSE residual structure may provide clues toward deciphering the protein folding code. This review focuses on recent advances in our understanding of the nature of DSE collapse under folding conditions, the quantification of the stability of residual structure in the DSE, the determination of the location and types of residues involved in thermodynamically significant residual structure and advances in detection of long-range interactions in the DSE.
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Affiliation(s)
- Bruce E Bowler
- Department of Chemistry and Biochemistry and Center for Biomolecular Structure and Dynamics, The University of Montana, Missoula, MT 59812, USA.
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40
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Camilloni C, Broglia RA, Tiana G. Hierarchy of folding and unfolding events of protein G,CI2, and ACBP from explicit-solvent simulations. J Chem Phys 2011; 134:045105. [DOI: 10.1063/1.3523345] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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41
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Sosnick TR, Barrick D. The folding of single domain proteins--have we reached a consensus? Curr Opin Struct Biol 2010; 21:12-24. [PMID: 21144739 DOI: 10.1016/j.sbi.2010.11.002] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2010] [Revised: 11/03/2010] [Accepted: 11/04/2010] [Indexed: 10/18/2022]
Abstract
Rather than stressing the most recent advances in the field, this review highlights the fundamental topics where disagreement remains and where adequate experimental data are lacking. These topics include properties of the denatured state and the role of residual structure, the nature of the fundamental steps and barriers, the extent of pathway heterogeneity and non-native interactions, recent comparisons between theory and experiment, and finally, dynamical properties of the folding reaction.
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Affiliation(s)
- Tobin R Sosnick
- Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
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