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Che X, Wu J, Liu H, Su J, Chen X. Cellular liquid-liquid phase separation: Concept, functions, regulations, and detections. J Cell Physiol 2023; 238:847-865. [PMID: 36870067 DOI: 10.1002/jcp.30980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 10/05/2022] [Accepted: 02/08/2023] [Indexed: 03/06/2023]
Abstract
Liquid-liquid phase separation is a multicomponent system separated into phases with different compositions and structures. It has been identified and explored in organisms after being introduced from the thermodynamic field. Condensate, the product of phase separation, exists in different scales of cellular structures, such as nucleolus, stress granules, and other organelles in nuclei or cytoplasm. And also play critical roles in different cellular behaviors. Here, we review the concept, thermodynamical and biochemical principles of phase separation. We summarized the main functions including the adjustment of biochemical reaction rates, the regulation of macromolecule folding state, subcellular structural support, the mediation of subcellular location, and intimately linked to different kinds of diseases, such as cancer and neurodegeneration. Advanced detection methods to investigate phase separation are collected and analyzed. We conclude with the discussion of anxiety of phase separation, and thought about how progress can be made to develop precise detection methods and disclose the potential application of condensates.
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Affiliation(s)
- Xuanlin Che
- Department of Dermatology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Skin Cancer and Psoriasis, Xiangya Hospital, Changsha, Hunan, China.,Hunan Engineering Research Center of Skin Health and Disease, Xiangya Hospital, Changsha, Hunan, China.,Xiangya Clinical Research Center for Cancer Immunotherapy, Central South University, Changsha, Hunan, China
| | - Jiajun Wu
- Department of Orthopaedics, Xiangya Hospital, Central South University, Changsha, China
| | - Hua Liu
- Department of Orthopaedics, Xiangya Hospital, Central South University, Changsha, China
| | - Juan Su
- Department of Dermatology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Skin Cancer and Psoriasis, Xiangya Hospital, Changsha, Hunan, China.,Hunan Engineering Research Center of Skin Health and Disease, Xiangya Hospital, Changsha, Hunan, China.,Xiangya Clinical Research Center for Cancer Immunotherapy, Central South University, Changsha, Hunan, China
| | - Xiang Chen
- Department of Dermatology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Skin Cancer and Psoriasis, Xiangya Hospital, Changsha, Hunan, China.,Hunan Engineering Research Center of Skin Health and Disease, Xiangya Hospital, Changsha, Hunan, China.,Xiangya Clinical Research Center for Cancer Immunotherapy, Central South University, Changsha, Hunan, China
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2
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Chan-Yao-Chong M, Durand D, Ha-Duong T. Molecular Dynamics Simulations Combined with Nuclear Magnetic Resonance and/or Small-Angle X-ray Scattering Data for Characterizing Intrinsically Disordered Protein Conformational Ensembles. J Chem Inf Model 2019; 59:1743-1758. [PMID: 30840442 DOI: 10.1021/acs.jcim.8b00928] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The concept of intrinsically disordered proteins (IDPs) has emerged relatively slowly, but over the past 20 years, it has become an intense research area in structural biology. Indeed, because of their considerable flexibility and structural heterogeneity, the determination of IDP conformational ensemble is particularly challenging and often requires a combination of experimental measurements and computational approaches. With the improved accuracy of all-atom force fields and the increasing computing performances, molecular dynamics (MD) simulations have become more and more reliable to generate realistic conformational ensembles. And the combination of MD simulations with experimental approaches, such as nuclear magnetic resonance (NMR) and/or small-angle X-ray scattering (SAXS) allows one to converge toward a more accurate and exhaustive description of IDP structures. In this Review, we discuss the state of the art of MD simulations of IDP conformational ensembles, with a special focus on studies that back-calculated and directly compared theoretical and experimental NMR or SAXS observables, such as chemical shifts (CS), 3J-couplings (3Jc), residual dipolar couplings (RDC), or SAXS intensities. We organize the review in three parts. In the first section, we discuss the studies which used NMR and/or SAXS data to test and validate the development of force fields or enhanced sampling techniques. In the second part, we explore different methods for the refinement of MD-derived structural ensembles, such as NMR or SAXS data-restrained MD simulations or ensemble reweighting to better fit experiments. Finally, we survey some recent studies combining MD simulations with NMR and/or SAXS measurements to investigate the relationship between IDP conformational ensemble and biological activity, as well as their implication in human diseases. From this review, we noticed that quite a few studies compared MD-generated conformational ensembles with both NMR and SAXS measurements to validate IDP structures at both local and global levels. Yet, beside the IDP propensity to form local secondary structures, their dynamic extension or compactness also appears important for their activity. Thus, we believe that a close synergy between MD simulations, NMR, and SAXS experiments would be greatly appropriate to address the challenges of characterizing the disordered structures of proteins and their complexes, relative to their biological functions.
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Affiliation(s)
- Maud Chan-Yao-Chong
- BioCIS, Université Paris-Sud, CNRS , Université Paris-Saclay , 92290 Châtenay-Malabry , France.,Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud , Université Paris-Saclay , 91198 , Gif-sur-Yvette cedex, France
| | - Dominique Durand
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud , Université Paris-Saclay , 91198 , Gif-sur-Yvette cedex, France
| | - Tâp Ha-Duong
- BioCIS, Université Paris-Sud, CNRS , Université Paris-Saclay , 92290 Châtenay-Malabry , France
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3
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A Metastable Contact and Structural Disorder in the Estrogen Receptor Transactivation Domain. Structure 2018; 27:229-240.e4. [PMID: 30581045 DOI: 10.1016/j.str.2018.10.026] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 09/06/2018] [Accepted: 10/25/2018] [Indexed: 11/23/2022]
Abstract
The N-terminal transactivation domain (NTD) of estrogen receptor alpha, a well-known member of the family of intrinsically disordered proteins, mediates the receptor's transactivation function. However, an accurate molecular dissection of NTD's structure-function relationships remains elusive. Here, we show that the NTD adopts a mostly disordered, unexpectedly compact conformation that undergoes structural expansion on chemical denaturation. By combining small-angle X-ray scattering, hydroxyl radical protein footprinting, and computational modeling, we derive the ensemble-structures of the NTD and determine its ensemble-contact map revealing metastable long-range contacts, e.g., between residues I33 and S118. We show that mutation at S118, a known phosphorylation site, promotes conformational changes and increases coactivator binding. We further demonstrate via fluorine-19 (19F) nuclear magnetic resonance that mutations near I33 alter 19F chemical shifts at S118, confirming the proposed I33-S118 contact in the ensemble of structural disorder. These findings extend our understanding of how specific contact metastability mediates critical functions of disordered proteins.
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4
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Bhattacharya S, Xu L, Thompson D. Revisiting the earliest signatures of amyloidogenesis: Roadmaps emerging from computational modeling and experiment. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2018. [DOI: 10.1002/wcms.1359] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Shayon Bhattacharya
- Department of Physics, Bernal InstituteUniversity of LimerickLimerickIreland
| | - Liang Xu
- Department of Physics, Bernal InstituteUniversity of LimerickLimerickIreland
| | - Damien Thompson
- Department of Physics, Bernal InstituteUniversity of LimerickLimerickIreland
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5
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Arefi HH, Yamamoto T. Communication: Self-assembly of a model supramolecular polymer studied by replica exchange with solute tempering. J Chem Phys 2017; 147:211102. [PMID: 29221407 DOI: 10.1063/1.5008275] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Conventional molecular-dynamics (cMD) simulation has a well-known limitation in accessible time and length scales, and thus various enhanced sampling techniques have been proposed to alleviate the problem. In this paper, we explore the utility of replica exchange with solute tempering (REST) (i.e., a variant of Hamiltonian replica exchange methods) to simulate the self-assembly of a supramolecular polymer in explicit solvent and compare the performance with temperature-based replica exchange MD (T-REMD) as well as cMD. As a test system, we consider a relatively simple all-atom model of supramolecular polymerization (namely, benzene-1,3,5-tricarboxamides in methylcyclohexane solvent). Our results show that both REST and T-REMD are able to predict highly ordered polymer structures with helical H-bonding patterns, in contrast to cMD which completely fails to obtain such a structure for the present model. At the same time, we have also experienced some technical challenge (i.e., aggregation-dispersion transition and the resulting bottleneck for replica traversal), which is illustrated numerically. Since the computational cost of REST scales more moderately than T-REMD, we expect that REST will be useful for studying the self-assembly of larger systems in solution with enhanced rearrangement of monomers.
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Affiliation(s)
- Hadi H Arefi
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Takeshi Yamamoto
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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6
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Lee KH, Chen J. Optimization of the GBMV2 implicit solvent force field for accurate simulation of protein conformational equilibria. J Comput Chem 2017; 38:1332-1341. [PMID: 28397268 DOI: 10.1002/jcc.24734] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2016] [Revised: 11/16/2016] [Accepted: 12/14/2016] [Indexed: 12/12/2022]
Abstract
Accurate treatment of solvent environment is critical for reliable simulations of protein conformational equilibria. Implicit treatment of solvation, such as using the generalized Born (GB) class of models arguably provides an optimal balance between computational efficiency and physical accuracy. Yet, GB models are frequently plagued by a tendency to generate overly compact structures. The physical origins of this drawback are relatively well understood, and the key to a balanced implicit solvent protein force field is careful optimization of physical parameters to achieve a sufficient level of cancellation of errors. The latter has been hampered by the difficulty of generating converged conformational ensembles of non-trivial model proteins using the popular replica exchange sampling technique. Here, we leverage improved sampling efficiency of a newly developed multi-scale enhanced sampling technique to re-optimize the generalized-Born with molecular volume (GBMV2) implicit solvent model with the CHARMM36 protein force field. Recursive optimization of key GBMV2 parameters (such as input radii) and protein torsion profiles (via the CMAP torsion cross terms) has led to a more balanced GBMV2 protein force field that recapitulates the structures and stabilities of both helical and β-hairpin model peptides. Importantly, this force field appears to be free of the over-compaction bias, and can generate structural ensembles of several intrinsically disordered proteins of various lengths that seem highly consistent with available experimental data. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Kuo Hao Lee
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, 66506
| | - Jianhan Chen
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, 66506
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7
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Olson MA. On the Helix Propensity in Generalized Born Solvent Descriptions of Modeling the Dark Proteome. Front Mol Biosci 2017; 4:3. [PMID: 28197405 PMCID: PMC5281587 DOI: 10.3389/fmolb.2017.00003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 01/12/2017] [Indexed: 01/06/2023] Open
Abstract
Intrinsically disordered proteins that populate the so-called “Dark Proteome” offer challenging benchmarks of atomistic simulation methods to accurately model conformational transitions on a multidimensional energy landscape. This work explores the application of parallel tempering with implicit solvent models as a computational framework to capture the conformational ensemble of an intrinsically disordered peptide derived from the Ebola virus protein VP35. A recent X-ray crystallographic study reported a protein-peptide interface where the VP35 peptide underwent a folding transition from a disordered form to a helix-β-turn-helix topological fold upon molecular association with the Ebola protein NP. An assessment is provided of the accuracy of two generalized Born solvent models (GBMV2 and GBSW2) using the CHARMM force field and applied with temperature-based replica exchange dynamics to calculate the disorder propensity of the peptide and its probability density of states in a continuum solvent. A further comparison is presented of applying an explicit/implicit solvent hybrid replica exchange simulation of the peptide to determine the effect of modeling water interactions at the all-atom resolution.
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Affiliation(s)
- Mark A Olson
- Department of Cell Biology and Biochemistry, Molecular and Translational Sciences Division, United States Army Medical Research Institute for Infectious Diseases Fredrick, MD, USA
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8
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Maximova T, Moffatt R, Ma B, Nussinov R, Shehu A. Principles and Overview of Sampling Methods for Modeling Macromolecular Structure and Dynamics. PLoS Comput Biol 2016; 12:e1004619. [PMID: 27124275 PMCID: PMC4849799 DOI: 10.1371/journal.pcbi.1004619] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Investigation of macromolecular structure and dynamics is fundamental to understanding how macromolecules carry out their functions in the cell. Significant advances have been made toward this end in silico, with a growing number of computational methods proposed yearly to study and simulate various aspects of macromolecular structure and dynamics. This review aims to provide an overview of recent advances, focusing primarily on methods proposed for exploring the structure space of macromolecules in isolation and in assemblies for the purpose of characterizing equilibrium structure and dynamics. In addition to surveying recent applications that showcase current capabilities of computational methods, this review highlights state-of-the-art algorithmic techniques proposed to overcome challenges posed in silico by the disparate spatial and time scales accessed by dynamic macromolecules. This review is not meant to be exhaustive, as such an endeavor is impossible, but rather aims to balance breadth and depth of strategies for modeling macromolecular structure and dynamics for a broad audience of novices and experts.
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Affiliation(s)
- Tatiana Maximova
- Department of Computer Science, George Mason University, Fairfax, Virginia, United States of America
| | - Ryan Moffatt
- Department of Computer Science, George Mason University, Fairfax, Virginia, United States of America
| | - Buyong Ma
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, Maryland, United States of America
| | - Ruth Nussinov
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, Maryland, United States of America
- Sackler Institute of Molecular Medicine, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Amarda Shehu
- Department of Computer Science, George Mason University, Fairfax, Virginia, United States of America
- Department of Biongineering, George Mason University, Fairfax, Virginia, United States of America
- School of Systems Biology, George Mason University, Manassas, Virginia, United States of America
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9
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Mitrea DM, Kriwacki RW. Phase separation in biology; functional organization of a higher order. Cell Commun Signal 2016; 14:1. [PMID: 26727894 PMCID: PMC4700675 DOI: 10.1186/s12964-015-0125-7] [Citation(s) in RCA: 469] [Impact Index Per Article: 58.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 12/29/2015] [Indexed: 12/18/2022] Open
Abstract
Inside eukaryotic cells, macromolecules are partitioned into membrane-bounded compartments and, within these, some are further organized into non-membrane-bounded structures termed membrane-less organelles. The latter structures are comprised of heterogeneous mixtures of proteins and nucleic acids and assemble through a phase separation phenomenon similar to polymer condensation. Membrane-less organelles are dynamic structures maintained through multivalent interactions that mediate diverse biological processes, many involved in RNA metabolism. They rapidly exchange components with the cellular milieu and their properties are readily altered in response to environmental cues, often implicating membrane-less organelles in responses to stress signaling. In this review, we discuss: (1) the functional roles of membrane-less organelles, (2) unifying structural and mechanistic principles that underlie their assembly and disassembly, and (3) established and emerging methods used in structural investigations of membrane-less organelles.
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Affiliation(s)
- Diana M Mitrea
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.
| | - Richard W Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, TN, 38163, USA.
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10
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Xia J, Flynn WF, Gallicchio E, Zhang BW, He P, Tan Z, Levy RM. Large-scale asynchronous and distributed multidimensional replica exchange molecular simulations and efficiency analysis. J Comput Chem 2015; 36:1772-85. [PMID: 26149645 PMCID: PMC4512903 DOI: 10.1002/jcc.23996] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 06/10/2015] [Accepted: 06/11/2015] [Indexed: 01/25/2023]
Abstract
We describe methods to perform replica exchange molecular dynamics (REMD) simulations asynchronously (ASyncRE). The methods are designed to facilitate large scale REMD simulations on grid computing networks consisting of heterogeneous and distributed computing environments as well as on homogeneous high-performance clusters. We have implemented these methods on NSF (National Science Foundation) XSEDE (Extreme Science and Engineering Discovery Environment) clusters and BOINC (Berkeley Open Infrastructure for Network Computing) distributed computing networks at Temple University and Brooklyn College at CUNY (the City University of New York). They are also being implemented on the IBM World Community Grid. To illustrate the methods, we have performed extensive (more than 60 ms in aggregate) simulations for the beta-cyclodextrin-heptanoate host-guest system in the context of one- and two-dimensional ASyncRE, and we used the results to estimate absolute binding free energies using the binding energy distribution analysis method. We propose ways to improve the efficiency of REMD simulations: these include increasing the number of exchanges attempted after a specified molecular dynamics (MD) period up to the fast exchange limit and/or adjusting the MD period to allow sufficient internal relaxation within each thermodynamic state. Although ASyncRE simulations generally require long MD periods (>picoseconds) per replica exchange cycle to minimize the overhead imposed by heterogeneous computing networks, we found that it is possible to reach an efficiency similar to conventional synchronous REMD, by optimizing the combination of the MD period and the number of exchanges attempted per cycle.
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Affiliation(s)
- Junchao Xia
- Center for Biophysics and Computational Biology, Department of Chemistry and Institute for Computational Molecular Science, Temple University, Philadelphia, PA 19122
| | - William F. Flynn
- Center for Biophysics and Computational Biology, Department of Chemistry and Institute for Computational Molecular Science, Temple University, Philadelphia, PA 19122
- Department of Physics & Astronomy, Rutgers University, Piscataway, NJ 08854
| | | | - Bin W. Zhang
- Center for Biophysics and Computational Biology, Department of Chemistry and Institute for Computational Molecular Science, Temple University, Philadelphia, PA 19122
| | - Peng He
- Center for Biophysics and Computational Biology, Department of Chemistry and Institute for Computational Molecular Science, Temple University, Philadelphia, PA 19122
| | - Zhiqiang Tan
- Department of Statistics, Rutgers University, Piscataway, NJ 08854
| | - Ronald M. Levy
- Center for Biophysics and Computational Biology, Department of Chemistry and Institute for Computational Molecular Science, Temple University, Philadelphia, PA 19122
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11
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Varadi M, Vranken W, Guharoy M, Tompa P. Computational approaches for inferring the functions of intrinsically disordered proteins. Front Mol Biosci 2015; 2:45. [PMID: 26301226 PMCID: PMC4525029 DOI: 10.3389/fmolb.2015.00045] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 07/21/2015] [Indexed: 01/09/2023] Open
Abstract
Intrinsically disordered proteins (IDPs) are ubiquitously involved in cellular processes and often implicated in human pathological conditions. The critical biological roles of these proteins, despite not adopting a well-defined fold, encouraged structural biologists to revisit their views on the protein structure-function paradigm. Unfortunately, investigating the characteristics and describing the structural behavior of IDPs is far from trivial, and inferring the function(s) of a disordered protein region remains a major challenge. Computational methods have proven particularly relevant for studying IDPs: on the sequence level their dependence on distinct characteristics determined by the local amino acid context makes sequence-based prediction algorithms viable and reliable tools for large scale analyses, while on the structure level the in silico integration of fundamentally different experimental data types is essential to describe the behavior of a flexible protein chain. Here, we offer an overview of the latest developments and computational techniques that aim to uncover how protein function is connected to intrinsic disorder.
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Affiliation(s)
- Mihaly Varadi
- Flemish Institute of Biotechnology Brussels, Belgium ; Department of Structural Biology, VIB, Vrije Universiteit Brussels Brussels, Belgium
| | - Wim Vranken
- Flemish Institute of Biotechnology Brussels, Belgium ; Department of Structural Biology, VIB, Vrije Universiteit Brussels Brussels, Belgium ; ULB-VUB - Interuniversity Institute of Bioinformatics in Brussels (IB)2 Brussels, Belgium
| | - Mainak Guharoy
- Flemish Institute of Biotechnology Brussels, Belgium ; Department of Structural Biology, VIB, Vrije Universiteit Brussels Brussels, Belgium
| | - Peter Tompa
- Flemish Institute of Biotechnology Brussels, Belgium ; Department of Structural Biology, VIB, Vrije Universiteit Brussels Brussels, Belgium
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12
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Lee KH, Chen J. Multiscale enhanced sampling of intrinsically disordered protein conformations. J Comput Chem 2015; 37:550-7. [PMID: 26052838 DOI: 10.1002/jcc.23957] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Revised: 05/03/2015] [Accepted: 05/11/2015] [Indexed: 12/24/2022]
Abstract
In a recently developed multiscale enhanced sampling (MSES) technique, topology-based coarse-grained (CG) models are coupled to atomistic force fields to enhance the sampling of atomistic protein conformations. Here, the MSES protocol is refined by designing more sophisticated Hamiltonian/temperature replica exchange schemes that involve additional parameters in the MSES coupling restraint potential, to more carefully control how conformations are coupled between the atomistic and CG models. A specific focus is to derive an optimal MSES protocol for simulating conformational ensembles of intrinsically disordered proteins (IDPs). The efficacy of the refined protocols, referred to as MSES-soft asymptote (SA), was evaluated using two model peptides with various levels of residual helicities. The results show that MSES-SA generates more reversible helix-coil transitions and leads to improved convergence on various ensemble conformational properties. This study further suggests that more detailed CG models are likely necessary for more effective sampling of local conformational transition of IDPs. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Kuo Hao Lee
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, 66506
| | - Jianhan Chen
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, 66506
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13
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Ganguly D, Chen J. Modulation of the disordered conformational ensembles of the p53 transactivation domain by cancer-associated mutations. PLoS Comput Biol 2015; 11:e1004247. [PMID: 25897952 PMCID: PMC4405366 DOI: 10.1371/journal.pcbi.1004247] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 03/17/2015] [Indexed: 11/18/2022] Open
Abstract
Intrinsically disordered proteins (IDPs) are frequently associated with human diseases such as cancers, and about one-fourth of disease-associated missense mutations have been mapped into predicted disordered regions. Understanding how these mutations affect the structure-function relationship of IDPs is a formidable task that requires detailed characterization of the disordered conformational ensembles. Implicit solvent coupled with enhanced sampling has been proposed to provide a balance between accuracy and efficiency necessary for systematic and comparative assessments of the effects of mutations as well as post-translational modifications on IDP structure and interaction. Here, we utilize a recently developed replica exchange with guided annealing enhanced sampling technique to calculate well-converged atomistic conformational ensembles of the intrinsically disordered transactivation domain (TAD) of tumor suppressor p53 and several cancer-associated mutants in implicit solvent. The simulations are critically assessed by quantitative comparisons with several types of experimental data that provide structural information on both secondary and tertiary levels. The results show that the calculated ensembles reproduce local structural features of wild-type p53-TAD and the effects of K24N mutation quantitatively. On the tertiary level, the simulated ensembles are overly compact, even though they appear to recapitulate the overall features of transient long-range contacts qualitatively. A key finding is that, while p53-TAD and its cancer mutants sample a similar set of conformational states, cancer mutants could introduce both local and long-range structural modulations to potentially perturb the balance of p53 binding to various regulatory proteins and further alter how this balance is regulated by multisite phosphorylation of p53-TAD. The current study clearly demonstrates the promise of atomistic simulations for detailed characterization of IDP conformations, and at the same time reveals important limitations in the current implicit solvent protein force field that must be sufficiently addressed for reliable description of long-range structural features of the disordered ensembles. Tumor suppressor p53 is the most frequently mutated protein in human cancers. Clinical studies have suggested that the type of p53 mutation can be linked to cancer prognosis, response to drug treatment, and patient survival. It is thus crucial to understand the molecular basis of p53 inactivation by various types of mutations, so as to understand the biological outcomes and assess potential cancer intervention strategies. Here, we utilize a recently developed replica exchange with guided annealing enhanced sampling technique to calculate well-converged atomistic conformational ensembles of the intrinsically disordered transactivation domain (TAD) of tumor suppressor p53 and several cancer-associated mutants in an implicit solvent protein force field. The calculated ensembles are in quantitative agreement with several types of existing NMR data on the wild-type protein and the K24N mutant. The results suggest that, while all sequences sample a similar set of conformational substates, cancer mutants could introduce both local and long-range structural modulations and in turn perturb the balance of p53 binding to various regulatory proteins and further alter how this balance is regulated by multisite phosphorylation of p53-TAD. The study also reveals important limitations in implicit solvent for simulations of disordered proteins like p53-TAD.
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Affiliation(s)
- Debabani Ganguly
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, United States of America
- Indian Institute of Engineering Science and Technology, Shibpur Howrah, India
- * E-mail: (DG); (JC)
| | - Jianhan Chen
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, United States of America
- * E-mail: (DG); (JC)
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