51
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Badasyan A, Mamasakhlisov YS, Podgornik R, Parsegian VA. Solvent effects in the helix-coil transition model can explain the unusual biophysics of intrinsically disordered proteins. J Chem Phys 2015; 143:014102. [DOI: 10.1063/1.4923292] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Artem Badasyan
- Materials Research Laboratory, University of Nova Gorica, Vipavska 13, SI-5000 Nova Gorica, Slovenia
| | - Yevgeni Sh. Mamasakhlisov
- Department of Molecular Physics, Yerevan State University, A. Manougian St. 1, 0025 Yerevan, Armenia
| | - Rudolf Podgornik
- Department of Theoretical Physics, J. Stefan Institute and Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana, Slovenia
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003-9337, USA
| | - V. Adrian Parsegian
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003-9337, USA
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52
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Li W, Kinch LN, Karplus PA, Grishin NV. ChSeq: A database of chameleon sequences. Protein Sci 2015; 24:1075-86. [PMID: 25970262 DOI: 10.1002/pro.2689] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 04/15/2015] [Accepted: 04/24/2015] [Indexed: 11/11/2022]
Abstract
Chameleon sequences (ChSeqs) refer to sequence strings of identical amino acids that can adopt different conformations in protein structures. Researchers have detected and studied ChSeqs to understand the interplay between local and global interactions in protein structure formation. The different secondary structures adopted by one ChSeq challenge sequence-based secondary structure predictors. With increasing numbers of available Protein Data Bank structures, we here identify a large set of ChSeqs ranging from 6 to 10 residues in length. The homologous ChSeqs discovered highlight the structural plasticity involved in biological function. When compared with previous studies, the set of unrelated ChSeqs found represents an about 20-fold increase in the number of detected sequences, as well as an increase in the longest ChSeq length from 8 to 10 residues. We applied secondary structure predictors on our ChSeqs and found that methods based on a sequence profile outperformed methods based on a single sequence. For the unrelated ChSeqs, the evolutionary information provided by the sequence profile typically allows successful prediction of the prevailing secondary structure adopted in each protein family. Our dataset will facilitate future studies of ChSeqs, as well as interpretations of the interplay between local and nonlocal interactions. A user-friendly web interface for this ChSeq database is available at prodata.swmed.edu/chseq.
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Affiliation(s)
- Wenlin Li
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas, 75390-9050.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, 75390-9050
| | - Lisa N Kinch
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, 75390-9050
| | - P Andrew Karplus
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon, 97331
| | - Nick V Grishin
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas, 75390-9050.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, 75390-9050.,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, 75390-9050
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53
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Soley M, Markmann A, Batista VS. Steered quantum dynamics for energy minimization. J Phys Chem B 2015; 119:715-27. [PMID: 25122515 DOI: 10.1021/jp5046723] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We introduce a quantum optimal control algorithm for energy minimization that combines the diffeomorphic modulation under observable response preserving homotopy (D-MORPH) gradient and the Broyden Fletcher Goldfarb Shanno (BFGS) iterative scheme for nonlinear optimization. An extended set of controls defining the time-dependent mass, dipole moment, and external perturbational field are optimized to find an effective Hamiltonian that steers the dynamics of the system into the global minimum without getting trapped into local minima. The algorithm is illustrated as applied to energy minimization on rugged surfaces and golf potentials comparable to those previously explored for testing quantum annealing methodologies.
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Affiliation(s)
- Micheline Soley
- Department of Chemistry, Yale University , P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
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54
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Wüst T, Reith D, Virnau P. Sequence determines degree of knottedness in a coarse-grained protein model. PHYSICAL REVIEW LETTERS 2015; 114:028102. [PMID: 25635563 DOI: 10.1103/physrevlett.114.028102] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2013] [Indexed: 06/04/2023]
Abstract
Knots are abundant in globular homopolymers but rare in globular proteins. To shed new light on this long-standing conundrum, we study the influence of sequence on the formation of knots in proteins under native conditions within the framework of the hydrophobic-polar lattice protein model. By employing large-scale Wang-Landau simulations combined with suitable Monte Carlo trial moves we show that even though knots are still abundant on average, sequence introduces large variability in the degree of self-entanglements. Moreover, we are able to design sequences which are either almost always or almost never knotted. Our findings serve as proof of concept that the introduction of just one additional degree of freedom per monomer (in our case sequence) facilitates evolution towards a protein universe in which knots are rare.
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Affiliation(s)
- Thomas Wüst
- Scientific IT Services, ETH Zürich, 8092 Zürich, Switzerland
| | - Daniel Reith
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 9, 55128 Mainz, Germany
| | - Peter Virnau
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 9, 55128 Mainz, Germany
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55
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Kurzbach D, Kontaxis G, Coudevylle N, Konrat R. NMR Spectroscopic Studies of the Conformational Ensembles of Intrinsically Disordered Proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 870:149-85. [PMID: 26387102 DOI: 10.1007/978-3-319-20164-1_5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Intrinsically disordered proteins (IDPs) are characterized by substantial conformational flexibility and thus not amenable to conventional structural biology techniques. Given their inherent structural flexibility NMR spectroscopy offers unique opportunities for structural and dynamic studies of IDPs. The past two decades have witnessed significant development of NMR spectroscopy that couples advances in spin physics and chemistry with a broad range of applications. This chapter will summarize key advances in NMR methodology. Despite the availability of efficient (multi-dimensional) NMR experiments for signal assignment of IDPs it is discussed that NMR of larger and more complex IDPs demands spectral simplification strategies capitalizing on specific isotope-labeling strategies. Prototypical applications of isotope labeling-strategies are described. Since IDP-ligand association and dissociation processes frequently occur on time scales that are amenable to NMR spectroscopy we describe in detail the application of CPMG relaxation dispersion techniques to studies of IDP protein binding. Finally, we demonstrate that the complementary usage of NMR and EPR data provide a more comprehensive picture about the conformational states of IDPs and can be employed to analyze the conformational ensembles of IDPs.
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Affiliation(s)
- Dennis Kurzbach
- Department of Computational and Structural Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030, Vienna, Austria
| | - Georg Kontaxis
- Department of Computational and Structural Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030, Vienna, Austria
| | - Nicolas Coudevylle
- Department of Computational and Structural Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030, Vienna, Austria
| | - Robert Konrat
- Department of Computational and Structural Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030, Vienna, Austria.
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56
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Baiz CR, Lin YS, Peng CS, Beauchamp KA, Voelz VA, Pande VS, Tokmakoff A. A molecular interpretation of 2D IR protein folding experiments with Markov state models. Biophys J 2014; 106:1359-70. [PMID: 24655511 DOI: 10.1016/j.bpj.2014.02.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 01/28/2014] [Accepted: 02/03/2014] [Indexed: 11/24/2022] Open
Abstract
The folding mechanism of the N-terminal domain of ribosomal protein L9 (NTL91-39) is studied using temperature-jump (T-jump) amide I' two-dimensional infrared (2D IR) spectroscopy in combination with spectral simulations based on a Markov state model (MSM) built from millisecond-long molecular dynamics trajectories. The results provide evidence for a compact well-structured folded state and a heterogeneous fast-exchanging denatured state ensemble exhibiting residual secondary structure. The folding rate of 26.4 μs(-1) (at 80°C), extracted from the T-jump response of NTL91-39, compares favorably with the 18 μs(-1) obtained from the MSM. Structural decomposition of the MSM and analysis along the folding coordinate indicates that helix-formation nucleates the global folding. Simulated difference spectra, corresponding to the global folding transition of the MSM, are in qualitative agreement with measured T-jump 2D IR spectra. The experiments demonstrate the use of T-jump 2D IR spectroscopy as a valuable tool for studying protein folding, with direct connections to simulations. The results suggest that in addition to predicting the correct native structure and folding time constant, molecular dynamics simulations carried out with modern force fields provide an accurate description of folding mechanisms in small proteins.
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Affiliation(s)
- Carlos R Baiz
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Yu-Shan Lin
- Department of Chemistry, Stanford University, Stanford, California
| | - Chunte Sam Peng
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | | | - Vincent A Voelz
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania
| | - Vijay S Pande
- Department of Chemistry, Stanford University, Stanford, California; Biophysics Program, Stanford University, Stanford, California; Department of Structural Biology, Stanford University, Stanford, California
| | - Andrei Tokmakoff
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts.
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57
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Sher I, Chang SC, Li Y, Chhabra S, Palmer AG, Norton RS, Chill JH. Conformational flexibility in the binding surface of the potassium channel blocker ShK. Chembiochem 2014; 15:2402-10. [PMID: 25236806 DOI: 10.1002/cbic.201402295] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Indexed: 01/27/2023]
Abstract
ShK is a 35-residue peptide that binds with high affinity to human voltage-gated potassium channels through a conserved K-Y dyad. Here we have employed NMR measurements of backbone-amide (15)N spin-relaxation rates to investigate motions of the ShK backbone. Although ShK is rigid on the ps to ns timescale, increased linewidths observed for 11 backbone-amide (15)N resonances identify chemical or conformational exchange contributions to the spin relaxation. Relaxation dispersion profiles indicate that exchange between major and minor conformers occurs on the sub-millisecond timescale. Affected residues are mostly clustered around the central helix-kink-helix structure and the critical K22-Y23 motif. We suggest that the less structured minor conformer increases the exposure of Y23, known to contribute to binding affinity and selectivity, thereby facilitating its interaction with potassium channels. These findings have potential implications for the design of new channel blockers based on ShK.
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Affiliation(s)
- Inbal Sher
- Department of Chemistry, Bar Ilan University, Ramat Gan 52900 (Israel)
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58
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High-pressure SANS and fluorescence unfolding study of calmodulin. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:1560-8. [DOI: 10.1016/j.bbapap.2014.05.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Revised: 05/06/2014] [Accepted: 05/16/2014] [Indexed: 11/15/2022]
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59
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Shi G, Vogel T, Wüst T, Li YW, Landau DP. Effect of single-site mutations on hydrophobic-polar lattice proteins. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:033307. [PMID: 25314564 DOI: 10.1103/physreve.90.033307] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Indexed: 06/04/2023]
Abstract
We developed a heuristic method for determining the ground-state degeneracy of hydrophobic-polar (HP) lattice proteins, based on Wang-Landau and multicanonical sampling. It is applied during comprehensive studies of single-site mutations in specific HP proteins with different sequences. The effects in which we are interested include structural changes in ground states, changes of ground-state energy, degeneracy, and thermodynamic properties of the system. With respect to mutations, both extremely sensitive and insensitive positions in the HP sequence have been found. That is, ground-state energies and degeneracies, as well as other thermodynamic and structural quantities, may be either largely unaffected or may change significantly due to mutation.
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Affiliation(s)
- Guangjie Shi
- Center for Simulational Physics, The University of Georgia, Athens, Georgia 30602, USA
| | - Thomas Vogel
- Theoretical Division (T-1), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Thomas Wüst
- Scientific IT Services, ETH Zürich IT Services, 8092 Zürich, Switzerland
| | - Ying Wai Li
- National Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - David P Landau
- Center for Simulational Physics, The University of Georgia, Athens, Georgia 30602, USA
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60
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Konrat R. NMR contributions to structural dynamics studies of intrinsically disordered proteins. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 241:74-85. [PMID: 24656082 PMCID: PMC3985426 DOI: 10.1016/j.jmr.2013.11.011] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 11/13/2013] [Accepted: 11/18/2013] [Indexed: 05/04/2023]
Abstract
Intrinsically disordered proteins (IDPs) are characterized by substantial conformational plasticity. Given their inherent structural flexibility X-ray crystallography is not applicable to study these proteins. In contrast, NMR spectroscopy offers unique opportunities for structural and dynamic studies of IDPs. The past two decades have witnessed significant development of NMR spectroscopy that couples advances in spin physics and chemistry with a broad range of applications. This article will summarize key advances in basic physical-chemistry and NMR methodology, outline their limitations and envision future R&D directions.
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Affiliation(s)
- Robert Konrat
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, A-1030 Vienna, Austria.
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61
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Samuel AZ, Umapathy S. Energy funneling and macromolecular conformational dynamics: a 2D Raman correlation study of PEG melting. Polym J 2014. [DOI: 10.1038/pj.2014.10] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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62
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Li H, Xie Y, Liu C, Liu S. Physicochemical bases for protein folding, dynamics, and protein-ligand binding. SCIENCE CHINA-LIFE SCIENCES 2014; 57:287-302. [PMID: 24554472 DOI: 10.1007/s11427-014-4617-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 09/27/2013] [Indexed: 01/02/2023]
Abstract
Proteins are essential parts of living organisms and participate in virtually every process within cells. As the genomic sequences for increasing number of organisms are completed, research into how proteins can perform such a variety of functions has become much more intensive because the value of the genomic sequences relies on the accuracy of understanding the encoded gene products. Although the static three-dimensional structures of many proteins are known, the functions of proteins are ultimately governed by their dynamic characteristics, including the folding process, conformational fluctuations, molecular motions, and protein-ligand interactions. In this review, the physicochemical principles underlying these dynamic processes are discussed in depth based on the free energy landscape (FEL) theory. Questions of why and how proteins fold into their native conformational states, why proteins are inherently dynamic, and how their dynamic personalities govern protein functions are answered. This paper will contribute to the understanding of structure-function relationship of proteins in the post-genome era of life science research.
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Affiliation(s)
- HuiMin Li
- School of Mathematics and Computer Science, Yunnan University of Nationalities, Kunming, 650500, China
- Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of Ministry of Education, Yunnan University, Kunming, 650091, China
| | - YueHui Xie
- Teaching and Research Section of Computer, Department of Basic Medical, Kunming Medical University, Kunming, 650031, China
- Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of Ministry of Education, Yunnan University, Kunming, 650091, China
| | - CiQuan Liu
- Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of Ministry of Education, Yunnan University, Kunming, 650091, China
- Southwest Biological Diversity Laboratory, Kunming Branch of Chinese Academy of Sciences, Kunming, 650223, China
| | - ShuQun Liu
- Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of Ministry of Education, Yunnan University, Kunming, 650091, China.
- Southwest Biological Diversity Laboratory, Kunming Branch of Chinese Academy of Sciences, Kunming, 650223, China.
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Kunming, 650091, China.
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63
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Compiani M, Capriotti E. Computational and theoretical methods for protein folding. Biochemistry 2013; 52:8601-24. [PMID: 24187909 DOI: 10.1021/bi4001529] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A computational approach is essential whenever the complexity of the process under study is such that direct theoretical or experimental approaches are not viable. This is the case for protein folding, for which a significant amount of data are being collected. This paper reports on the essential role of in silico methods and the unprecedented interplay of computational and theoretical approaches, which is a defining point of the interdisciplinary investigations of the protein folding process. Besides giving an overview of the available computational methods and tools, we argue that computation plays not merely an ancillary role but has a more constructive function in that computational work may precede theory and experiments. More precisely, computation can provide the primary conceptual clues to inspire subsequent theoretical and experimental work even in a case where no preexisting evidence or theoretical frameworks are available. This is cogently manifested in the application of machine learning methods to come to grips with the folding dynamics. These close relationships suggested complementing the review of computational methods within the appropriate theoretical context to provide a self-contained outlook of the basic concepts that have converged into a unified description of folding and have grown in a synergic relationship with their computational counterpart. Finally, the advantages and limitations of current computational methodologies are discussed to show how the smart analysis of large amounts of data and the development of more effective algorithms can improve our understanding of protein folding.
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Affiliation(s)
- Mario Compiani
- School of Sciences and Technology, University of Camerino , Camerino, Macerata 62032, Italy
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64
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Candelaresi M, Ragnoni E, Cappelli C, Corozzi A, Lima M, Monti S, Mennucci B, Nuti F, Papini AM, Foggi P. Conformational analysis of Gly-Ala-NHMe in D(2)O and DMSO solutions: a two-dimensional infrared spectroscopy study. J Phys Chem B 2013; 117:14226-37. [PMID: 24164089 DOI: 10.1021/jp406139t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A relevant number of experiments on short peptides has been performed in recent years. One of the major problems rises from the simultaneous presence of slightly different conformers at equilibrium in solution. In the present paper, the conformational characteristics of the Gly-l-Ala-Methyl amide dipeptide in D2O and DMSO solutions are investigated by nonlinear IR spectroscopy. The pump-probe scheme with ultrashort mid-infrared pulses, in the Amide I region, is used to determine the mutual orientation of the two C═O bonds and the dynamics due to solute-solvent interactions. The coupling between Amide I modes is evaluated from both linear and 2D spectra. The interconversion between the different conformations occurs on time scales longer than the vibrational lifetime, and the spectral diffusion observed in 2D spectra is attributed to the solvent dynamics. Quantum mechanical calculations and molecular dynamics simulations are performed to identify the most stable geometries. By comparing the experimental and the theoretical data, we establish the prevalence of β-like polar conformers in both water and DMSO solvents.
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Affiliation(s)
- Marco Candelaresi
- Heriot-Watt University, Edinburgh Campus , Edinburgh, Scotland EH14 4AS
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65
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Qiu S, Lin Z, Zhou Y, Li R, Zhang J, Zhang D, Luo L, Guo L, Qiu B, Chen G. Label-Free Fluorometric Method for Monitoring Conformational Flexibility of Laccase Based on a Selective Laccase Sensor. Anal Chem 2013; 85:11041-6. [DOI: 10.1021/ac402693k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Suyan Qiu
- Institute for Quality & Safety and Standards of Agricultural Products Research, Jiangxi Academy of Agricultural Sciences, Nanchang, Jiangxi, 330200, China
| | - Zhenyu Lin
- MOE
Key Laboratory of Analysis and Detection for Food Safety, Fujian Provincial
Key Laboratory of Analysis and Detection Technology for Food Safety,
Department of Chemistry, Fuzhou University, Fuzhou, Fujian, 350002, China
| | - Yaomin Zhou
- Institute for Quality & Safety and Standards of Agricultural Products Research, Jiangxi Academy of Agricultural Sciences, Nanchang, Jiangxi, 330200, China
| | - Ruili Li
- Institute for Quality & Safety and Standards of Agricultural Products Research, Jiangxi Academy of Agricultural Sciences, Nanchang, Jiangxi, 330200, China
| | - Jinyan Zhang
- Institute for Quality & Safety and Standards of Agricultural Products Research, Jiangxi Academy of Agricultural Sciences, Nanchang, Jiangxi, 330200, China
| | - Dawen Zhang
- Institute for Quality & Safety and Standards of Agricultural Products Research, Jiangxi Academy of Agricultural Sciences, Nanchang, Jiangxi, 330200, China
| | - Linguang Luo
- Institute for Quality & Safety and Standards of Agricultural Products Research, Jiangxi Academy of Agricultural Sciences, Nanchang, Jiangxi, 330200, China
| | - Longhua Guo
- MOE
Key Laboratory of Analysis and Detection for Food Safety, Fujian Provincial
Key Laboratory of Analysis and Detection Technology for Food Safety,
Department of Chemistry, Fuzhou University, Fuzhou, Fujian, 350002, China
| | - Bin Qiu
- MOE
Key Laboratory of Analysis and Detection for Food Safety, Fujian Provincial
Key Laboratory of Analysis and Detection Technology for Food Safety,
Department of Chemistry, Fuzhou University, Fuzhou, Fujian, 350002, China
| | - Guonan Chen
- MOE
Key Laboratory of Analysis and Detection for Food Safety, Fujian Provincial
Key Laboratory of Analysis and Detection Technology for Food Safety,
Department of Chemistry, Fuzhou University, Fuzhou, Fujian, 350002, China
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66
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Abstract
According to Thomas Kuhn, the success of 'normal science,' the science we all practice on a daily basis, depends on the adherence to, and practice of, a paradigm accepted by the scientific community. When great scientific upheavals occur, they involve the rejection of the current paradigm in favor of a new paradigm that better integrates the facts available and better predicts the behavior of a particular scientific system. In the field of Alzheimer's disease, a recent example of such a paradigm shift has been the apparent rejection of the 'amyloid cascade hypothesis,' promulgated by Hardy and Higgins in 1992 to explain the etiology of Alzheimer's disease, in favor of what has been referred to as the 'oligomer cascade hypothesis'. This paradigm shift has been breathtaking in its rapidity, its pervasiveness in the Alzheimer's disease field, and its adoption in an increasing number of other fields, including those of Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and the prionoses. However, these facts do not mean, a priori, that the experiments extant, and any re-interpretation of them, should be accepted by rote as support for the new paradigm. In the discussion that follows, I consider the foundational studies leading to the oligomer cascade hypothesis and evaluate the current state of the paradigm. I argue here that, more often than not, insufficient rigor has been applied in studies upon which this new paradigm has been based. Confusion, rather than clarity, has resulted. If the field is to make progress forward using as its paradigmatic basis amyloid β-protein oligomerization, then an epistemological re-evaluation of the amyloid β-protein oligomer system is required.
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Affiliation(s)
- David B Teplow
- Department of Neurology, David Geffen School of Medicine at UCLA, 635 Charles E. Young Dr. South, Room 445, Los Angeles, CA 90095, USA
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67
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Kundrotas PJ, Vakser IA. Protein-protein alternative binding modes do not overlap. Protein Sci 2013; 22:1141-5. [PMID: 23775945 DOI: 10.1002/pro.2295] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Revised: 06/01/2013] [Accepted: 06/03/2013] [Indexed: 11/09/2022]
Abstract
Proteins often bind other proteins in more than one way. Thus alternative binding modes is an essential feature of protein interactions. Such binding modes may be detected by X-ray crystallography and thus reflected in Protein Data Bank. The alternative binding is often observed not for the protein itself but for its structural homolog. The results of this study based on the analysis of a comprehensive set of co-crystallized protein-protein complexes show that the alternative binding modes generally do not overlap, but are spatially separated. This effect is based on molecular recognition characteristics of the protein structures. The results are also in excellent agreement with the intermolecular energy funnel size estimates obtained previously by an independent methodology. The results provide an important insight into the principles of protein association, as well as potential guidelines for modeling of protein complexes and the design of protein interfaces.
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Affiliation(s)
- Petras J Kundrotas
- Center for Bioinformatics and Department of Molecular Biosciences, The University of Kansas, Lawrence, Kansas 66047, USA
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68
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Dagan S, Hagai T, Gavrilov Y, Kapon R, Levy Y, Reich Z. Stabilization of a protein conferred by an increase in folded state entropy. Proc Natl Acad Sci U S A 2013; 110:10628-33. [PMID: 23754389 PMCID: PMC3696814 DOI: 10.1073/pnas.1302284110] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Entropic stabilization of native protein structures typically relies on strategies that serve to decrease the entropy of the unfolded state. Here we report, using a combination of experimental and computational approaches, on enhanced thermodynamic stability conferred by an increase in the configurational entropy of the folded state. The enhanced stability is observed upon modifications of a loop region in the enzyme acylphosphatase and is achieved despite significant enthalpy losses. The modifications that lead to increased stability, as well as those that result in destabilization, however, strongly compromise enzymatic activity, rationalizing the preservation of the native loop structure even though it does not provide the protein with maximal stability or kinetic foldability.
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Affiliation(s)
| | - Tzachi Hagai
- Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yulian Gavrilov
- Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | | | - Yaakov Levy
- Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ziv Reich
- Departments of Biological Chemistry and
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69
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Guilloux A, Caudron B, Jestin JL. A method to predict edge strands in beta-sheets from protein sequences. Comput Struct Biotechnol J 2013; 7:e201305001. [PMID: 24688737 PMCID: PMC3962219 DOI: 10.5936/csbj.201305001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 05/27/2013] [Accepted: 05/30/2013] [Indexed: 12/15/2022] Open
Abstract
There is a need for rules allowing three-dimensional structure information to be derived from protein sequences. In this work, consideration of an elementary protein folding step allows protein sub-sequences which optimize folding to be derived for any given protein sequence. Classical mechanics applied to this system and the energy conservation law during the elementary folding step yields an equation whose solutions are taken over the field of rational numbers. This formalism is applied to beta-sheets containing two edge strands and at least two central strands. The number of protein sub-sequences optimized for folding per amino acid in beta-strands is shown in particular to predict edge strands from protein sequences. Topological information on beta-strands and loops connecting them is derived for protein sequences with a prediction accuracy of 75%. The statistical significance of the finding is given. Applications in protein structure prediction are envisioned such as for the quality assessment of protein structure models.
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Affiliation(s)
- Antonin Guilloux
- Analyse algébrique, Institut de Mathématiques de Jussieu, Université Pierre et Marie Curie, Paris VI, France
| | - Bernard Caudron
- Centre d'Informatique pour la Biologie, Institut Pasteur, Paris, France
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70
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Kuzu G, Gursoy A, Nussinov R, Keskin O. Exploiting conformational ensembles in modeling protein-protein interactions on the proteome scale. J Proteome Res 2013; 12:2641-53. [PMID: 23590674 PMCID: PMC3685852 DOI: 10.1021/pr400006k] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cellular functions are performed through protein-protein interactions; therefore, identification of these interactions is crucial for understanding biological processes. Recent studies suggest that knowledge-based approaches are more useful than "blind" docking for modeling at large scales. However, a caveat of knowledge-based approaches is that they treat molecules as rigid structures. The Protein Data Bank (PDB) offers a wealth of conformations. Here, we exploited an ensemble of the conformations in predictions by a knowledge-based method, PRISM. We tested "difficult" cases in a docking-benchmark data set, where the unbound and bound protein forms are structurally different. Considering alternative conformations for each protein, the percentage of successfully predicted interactions increased from ~26 to 66%, and 57% of the interactions were successfully predicted in an "unbiased" scenario, in which data related to the bound forms were not utilized. If the appropriate conformation, or relevant template interface, is unavailable in the PDB, PRISM could not predict the interaction successfully. The pace of the growth of the PDB promises a rapid increase of ensemble conformations emphasizing the merit of such knowledge-based ensemble strategies for higher success rates in protein-protein interaction predictions on an interactome scale. We constructed the structural network of ERK interacting proteins as a case study.
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Affiliation(s)
- Guray Kuzu
- Center for Computational Biology and Bioinformatics and College of Engineering, Koc University Rumelifeneri Yolu, 34450 Sariyer Istanbul, Turkey
| | - Attila Gursoy
- Center for Computational Biology and Bioinformatics and College of Engineering, Koc University Rumelifeneri Yolu, 34450 Sariyer Istanbul, Turkey
| | - Ruth Nussinov
- Basic Science Program, SAIC-Frederick, Inc. National Cancer Institute, Center for Cancer Research Nanobiology Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702
- Sackler Inst. of Molecular Medicine Department of Human Genetics and Molecular Medicine Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ozlem Keskin
- Center for Computational Biology and Bioinformatics and College of Engineering, Koc University Rumelifeneri Yolu, 34450 Sariyer Istanbul, Turkey
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71
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Ruvinsky AM, Kirys T, Tuzikov AV, Vakser IA. Ensemble-based characterization of unbound and bound states on protein energy landscape. Protein Sci 2013; 22:734-44. [PMID: 23526684 DOI: 10.1002/pro.2256] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2012] [Revised: 02/02/2013] [Accepted: 03/15/2013] [Indexed: 11/07/2022]
Abstract
Physicochemical description of numerous cell processes is fundamentally based on the energy landscapes of protein molecules involved. Although the whole energy landscape is difficult to reconstruct, increased attention to particular targets has provided enough structures for mapping functionally important subspaces associated with the unbound and bound protein structures. The subspace mapping produces a discrete representation of the landscape, further called energy spectrum. We compiled and characterized ensembles of bound and unbound conformations of six small proteins and explored their spectra in implicit solvent. First, the analysis of the unbound-to-bound changes points to conformational selection as the binding mechanism for four proteins. Second, results show that bound and unbound spectra often significantly overlap. Moreover, the larger the overlap the smaller the root mean square deviation (RMSD) between the bound and unbound conformational ensembles. Third, the center of the unbound spectrum has a higher energy than the center of the corresponding bound spectrum of the dimeric and multimeric states for most of the proteins. This suggests that the unbound states often have larger entropy than the bound states. Fourth, the exhaustively long minimization, making small intrarotamer adjustments (all-atom RMSD ≤ 0.7 Å), dramatically reduces the distance between the centers of the bound and unbound spectra as well as the spectra extent. It condenses unbound and bound energy levels into a thin layer at the bottom of the energy landscape with the energy spacing that varies between 0.8-4.6 and 3.5-10.5 kcal/mol for the unbound and bound states correspondingly. Finally, the analysis of protein energy fluctuations showed that protein vibrations itself can excite the interstate transitions, including the unbound-to-bound ones.
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Affiliation(s)
- Anatoly M Ruvinsky
- Center for Bioinformatics, The University of Kansas, Lawrence, Kansas 66047, USA.
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72
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Abstract
When an amino-acid sequence cannot be optimized for both folding and function, folding can get compromised in favor of function. To understand this tradeoff better, we devise a novel method for extracting the "function-less" folding-motif of a protein fold from a set of structurally similar but functionally diverse proteins. We then obtain the β-trefoil folding-motif, and study its folding using structure-based models and molecular dynamics simulations. CompariA protein sequence serves two purpson with the folding of wild-type β-trefoil proteins shows that function affects folding in two ways: In the slower folding interleukin-1β, binding sites make the fold more complex, increase contact order and slow folding. In the faster folding hisactophilin, residues which could have been part of the folding-motif are used for function. This reduces the density of native contacts in functional regions and increases folding rate. The folding-motif helps identify subtle structural deviations which perturb folding. These may then be used for functional annotation. Further, the folding-motif could potentially be used as a first step in the sequence design of function-less scaffold proteins. Desired function can then be engineered into these scaffolds.
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Affiliation(s)
- Shachi Gosavi
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India.
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73
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Yuzlenko O, Lazaridis T. Membrane protein native state discrimination by implicit membrane models. J Comput Chem 2013; 34:731-8. [PMID: 23224861 PMCID: PMC3584241 DOI: 10.1002/jcc.23189] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 10/16/2012] [Accepted: 10/28/2012] [Indexed: 02/01/2023]
Abstract
Four implicit membrane models [IMM1, generalized Born (GB)-surface area-implicit membrane (GBSAIM), GB with a simple switching (GBSW), and heterogeneous dielectric GB (HDGB)] were tested for their ability to discriminate the native conformation of five membrane proteins from 450 decoys generated by the Rosetta-Membrane program. The energy ranking of the native state and Z-scores were used to assess the performance of the models. The effect of membrane thickness was examined and was found to be substantial. Quite satisfactory discrimination was achieved with the all-atom IMM1 and GBSW models at 25.4 Å thickness and with the HDGB model at 28.5 Å thickness. The energy components by themselves were not discriminative. Both van der Waals and electrostatic interactions contributed to native state discrimination, to a different extent in each model. Computational efficiency of the models decreased in the order: extended-atom IMM1 > all-atom IMM1 > GBSAIM > GBSW > HDGB. These results encourage the further development and use of implicit membrane models for membrane protein structure prediction.
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Affiliation(s)
- Olga Yuzlenko
- Department of Chemistry, City College of the City University of New York, 160 Convent Avenue, New York, New York 10031, USA
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74
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Yang LQ, Sang P, Tao Y, Fu YX, Zhang KQ, Xie YH, Liu SQ. Protein dynamics and motions in relation to their functions: several case studies and the underlying mechanisms. J Biomol Struct Dyn 2013; 32:372-93. [PMID: 23527883 PMCID: PMC3919177 DOI: 10.1080/07391102.2013.770372] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Proteins are dynamic entities in cellular solution with functions governed essentially by their dynamic personalities. We review several dynamics studies on serine protease proteinase K and HIV-1 gp120 envelope glycoprotein to demonstrate the importance of investigating the dynamic behaviors and molecular motions for a complete understanding of their structure–function relationships. Using computer simulations and essential dynamic (ED) analysis approaches, the dynamics data obtained revealed that: (i) proteinase K has highly flexible substrate-binding site, thus supporting the induced-fit or conformational selection mechanism of substrate binding; (ii) Ca2+ removal from proteinase K increases the global conformational flexibility, decreases the local flexibility of substrate-binding region, and does not influence the thermal motion of catalytic triad, thus explaining the experimentally determined decreased thermal stability, reduced substrate affinity, and almost unchanged catalytic activity upon Ca2+ removal; (iii) substrate binding affects the large concerted motions of proteinase K, and the resulting dynamic pocket can be connected to substrate binding, orientation, and product release; (iv) amino acid mutations 375 S/W and 423 I/P of HIV-1 gp120 have distinct effects on molecular motions of gp120, facilitating 375 S/W mutant to assume the CD4-bound conformation, while 423 I/P mutant to prefer for CD4-unliganded state. The mechanisms underlying protein dynamics and protein–ligand binding, including the concept of the free energy landscape (FEL) of the protein–solvent system, how the ruggedness and variability of FEL determine protein's dynamics, and how the three ligand-binding models, the lock-and-key, induced-fit, and conformational selection are rationalized based on the FEL theory are discussed in depth.
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Affiliation(s)
- Li-Quan Yang
- a Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education , Yunnan University , Kunming , 650091 , P.R. China
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75
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Where soft matter meets living matter--protein structure, stability, and folding in the cell. Curr Opin Struct Biol 2013; 23:212-7. [PMID: 23474325 DOI: 10.1016/j.sbi.2013.02.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Revised: 02/08/2013] [Accepted: 02/13/2013] [Indexed: 01/06/2023]
Abstract
A protein is a biopolymer that self-assembles through the process of protein folding. A cell is a crowded space where the surrounding macromolecules of a protein can limit the number of ways of folding. These crowding macromolecules can also affect the shape and the size of a physically malleable, or 'soft, squishy', protein with regulatory purposes. In this review, we focus on the in silico approaches of coarse-grained molecular simulations that enable the investigation of protein folding in a cell-like environment. When these simulation results were compared with experimentally measured properties of a protein, such joint effort has yielded new ideas on the specific function of a protein in cells. We also highlighted the recent developments of computer modeling and simulations that encompass the importance of the shape of a macromolecule, the interactions between macromolecules, and the hydrodynamic interactions on the kinetics and thermodynamics of a protein in a high concentration of protein solution and in cytoplasmic environments.
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76
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Global stability of protein folding from an empirical free energy function. J Theor Biol 2013; 321:44-53. [DOI: 10.1016/j.jtbi.2012.12.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 10/25/2012] [Accepted: 12/29/2012] [Indexed: 11/18/2022]
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77
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Folding of a heterogeneous β-hairpin peptide from temperature-jump 2D IR spectroscopy. Proc Natl Acad Sci U S A 2013; 110:2828-33. [PMID: 23382249 DOI: 10.1073/pnas.1211968110] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We provide a time- and structure-resolved characterization of the folding of the heterogeneous β-hairpin peptide Tryptophan Zipper 2 (Trpzip2) using 2D IR spectroscopy. The amide I' vibrations of three Trpzip2 isotopologues are used as a local probe of the midstrand contacts, β-turn, and overall β-sheet content. Our experiments distinguish between a folded state with a type I' β-turn and a misfolded state with a bulged turn, providing evidence for distinct conformations of the peptide backbone. Transient 2D IR spectroscopy at 45 °C following a laser temperature jump tracks the nanosecond and microsecond kinetics of unfolding and the exchange between conformers. Hydrogen bonds to the peptide backbone are loosened rapidly compared with the 5-ns temperature jump. Subsequently, all relaxation kinetics are characterized by an observed 1.2 ± 0.2-μs exponential. Our time-dependent 2D IR spectra are explained in terms of folding of either native or nonnative contacts from a common compact disordered state. Conversion from the disordered state to the folded state is consistent with a zip-out folding mechanism.
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78
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Limiting assumptions in molecular modeling: electrostatics. J Comput Aided Mol Des 2013; 27:107-14. [PMID: 23354627 DOI: 10.1007/s10822-013-9634-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 01/15/2013] [Indexed: 10/27/2022]
Abstract
Molecular mechanics attempts to represent intermolecular interactions in terms of classical physics. Initial efforts assumed a point charge located at the atom center and coulombic interactions. It is been recognized over multiple decades that simply representing electrostatics with a charge on each atom failed to reproduce the electrostatic potential surrounding a molecule as estimated by quantum mechanics. Molecular orbitals are not spherically symmetrical, an implicit assumption of monopole electrostatics. This perspective reviews recent evidence that requires use of multipole electrostatics and polarizability in molecular modeling.
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79
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Drobnak I, De Jonge N, Haesaerts S, Vesnaver G, Loris R, Lah J. Energetic Basis of Uncoupling Folding from Binding for an Intrinsically Disordered Protein. J Am Chem Soc 2013; 135:1288-94. [DOI: 10.1021/ja305081b] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Igor Drobnak
- Department of Physical Chemistry,
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, 1000 Ljubljana, Slovenia
| | - Natalie De Jonge
- Molecular Recognition Unit,
Department of Structural Biology, VIB,
Pleinlaan 2, B-1050 Brussel, Belgium
- Structural Biology Brussels, Department
of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Sarah Haesaerts
- Molecular Recognition Unit,
Department of Structural Biology, VIB,
Pleinlaan 2, B-1050 Brussel, Belgium
- Structural Biology Brussels, Department
of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Gorazd Vesnaver
- Department of Physical Chemistry,
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, 1000 Ljubljana, Slovenia
| | - Remy Loris
- Molecular Recognition Unit,
Department of Structural Biology, VIB,
Pleinlaan 2, B-1050 Brussel, Belgium
- Structural Biology Brussels, Department
of Biotechnology, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium
| | - Jurij Lah
- Department of Physical Chemistry,
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, 1000 Ljubljana, Slovenia
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80
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Unusual biophysics of intrinsically disordered proteins. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1834:932-51. [PMID: 23269364 DOI: 10.1016/j.bbapap.2012.12.008] [Citation(s) in RCA: 413] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 11/21/2012] [Accepted: 12/12/2012] [Indexed: 02/08/2023]
Abstract
Research of a past decade and a half leaves no doubt that complete understanding of protein functionality requires close consideration of the fact that many functional proteins do not have well-folded structures. These intrinsically disordered proteins (IDPs) and proteins with intrinsically disordered protein regions (IDPRs) are highly abundant in nature and play a number of crucial roles in a living cell. Their functions, which are typically associated with a wide range of intermolecular interactions where IDPs possess remarkable binding promiscuity, complement functional repertoire of ordered proteins. All this requires a close attention to the peculiarities of biophysics of these proteins. In this review, some key biophysical features of IDPs are covered. In addition to the peculiar sequence characteristics of IDPs these biophysical features include sequential, structural, and spatiotemporal heterogeneity of IDPs; their rough and relatively flat energy landscapes; their ability to undergo both induced folding and induced unfolding; the ability to interact specifically with structurally unrelated partners; the ability to gain different structures at binding to different partners; and the ability to keep essential amount of disorder even in the bound form. IDPs are also characterized by the "turned-out" response to the changes in their environment, where they gain some structure under conditions resulting in denaturation or even unfolding of ordered proteins. It is proposed that the heterogeneous spatiotemporal structure of IDPs/IDPRs can be described as a set of foldons, inducible foldons, semi-foldons, non-foldons, and unfoldons. They may lose their function when folded, and activation of some IDPs is associated with the awaking of the dormant disorder. It is possible that IDPs represent the "edge of chaos" systems which operate in a region between order and complete randomness or chaos, where the complexity is maximal. This article is part of a Special Issue entitled: The emerging dynamic view of proteins: Protein plasticity in allostery, evolution and self-assembly.
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81
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Wei W, Yu J, Broomell C, Israelachvili JN, Waite JH. Hydrophobic enhancement of Dopa-mediated adhesion in a mussel foot protein. J Am Chem Soc 2012; 135:377-83. [PMID: 23214725 DOI: 10.1021/ja309590f] [Citation(s) in RCA: 156] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dopa (3,4-dihydroxyphenylalanine) is recognized as a key chemical signature of mussel adhesion and has been adopted into diverse synthetic polymer systems. Dopa's notorious susceptibility to oxidation, however, poses significant challenges to the practical translation of mussel adhesion. Using a surface forces apparatus to investigate the adhesion of mussel foot protein 3 (Mfp3) "slow", a hydrophobic protein variant of the Mfp3 family in the plaque, we have discovered a subtle molecular strategy correlated with hydrophobicity that appears to compensate for Dopa instability. At pH 3, where Dopa is stable, Mfp3 slow, like Mfp3 "fast" adhesion to mica, is directly proportional to the mol % of Dopa present in the protein. At pH of 5.5 and 7.5, however, loss of adhesion in Mfp3 slow was less than half that occurring in Mfp3 fast, purportedly because Dopa in Mfp3 slow is less prone to oxidation. Indeed, cyclic voltammetry showed that the oxidation potential of Dopa in Mfp3 slow is significantly higher than in Mfp3 fast at pH of 7.5. A much greater difference between the two variants was revealed in the interaction energy of two symmetric Mfp3 slow films (E(ad) = -3 mJ/m(2)). This energy corresponds to the energy of protein cohesion which is notable for its reversibility and pH independence. Exploitation of aromatic hydrophobic sequences to protect Dopa against oxidation as well as to mediate hydrophobic and H-bonding interactions between proteins provides new insights for developing effective artificial underwater adhesives.
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Affiliation(s)
- Wei Wei
- Materials Research Laboratory, University of California, Santa Barbara, California 93106, United States
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82
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Narasimhan SL, Rajarajan AK, Vardharaj L. HP-sequence design for lattice proteins—An exact enumeration study on diamond as well as square lattice. J Chem Phys 2012; 137:115102. [DOI: 10.1063/1.4752479] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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83
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Kurzbach D, Schömer M, Wilms VS, Frey H, Hinderberger D. How Structure-Related Collapse Mechanisms Determine Nanoscale Inhomogeneities in Thermoresponsive Polymers. Macromolecules 2012. [DOI: 10.1021/ma3014299] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Dennis Kurzbach
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz,
Germany
| | - Martina Schömer
- Department of Organic
Chemistry, Johannes Gutenberg-University Mainz, Duesbergweg 10-14,
55128 Mainz, Germany
| | - Valerie S. Wilms
- Department of Organic
Chemistry, Johannes Gutenberg-University Mainz, Duesbergweg 10-14,
55128 Mainz, Germany
- Graduate School “Materials Science in Mainz”, Staudingerweg 9, 55099 Mainz,
Germany
| | - Holger Frey
- Department of Organic
Chemistry, Johannes Gutenberg-University Mainz, Duesbergweg 10-14,
55128 Mainz, Germany
| | - Dariush Hinderberger
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz,
Germany
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84
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Estácio SG, Fernandes CS, Krobath H, Faísca PFN, Shakhnovich EI. Robustness of atomistic Gō models in predicting native-like folding intermediates. J Chem Phys 2012; 137:085102. [DOI: 10.1063/1.4747492] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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85
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Wüst T, Landau DP. Optimized Wang-Landau sampling of lattice polymers: Ground state search and folding thermodynamics of HP model proteins. J Chem Phys 2012; 137:064903. [DOI: 10.1063/1.4742969] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
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86
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Abstract
Attempts to answer the Levinthal question "How proteins fold to give such a unique structure" are discussed. In the first part of this article, we focus on a few reasons as to why the solution to the protein-folding problem (PFP) has been elusive for a very long time. One is a result of the misinterpretation of Anfinsen's Thermodynamic hypothesis which led to the conclusion that the native structure of a protein must be at a global minimum of the Gibbs energy. The second is the result of the adherence to the hydrophobic paradigm, and at the same time ignoring a whole repertoire of hydrophilic effects. It is argued that switching from a target-based to a caused-based approach, and adopting the hydrophilic paradigm leads straightforwardly to a simple answer to Levinthal's question, as well as to a solution of the PFP.
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Affiliation(s)
- Arieh Ben-Naim
- Department of Physical Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel.
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87
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Chellapa GD, Rose GD. Reducing the dimensionality of the protein-folding search problem. Protein Sci 2012; 21:1231-40. [PMID: 22692765 DOI: 10.1002/pro.2106] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 06/04/2012] [Accepted: 06/05/2012] [Indexed: 11/10/2022]
Abstract
How does a folding protein negotiate a vast, featureless conformational landscape and adopt its native structure in biological real time? Motivated by this search problem, we developed a novel algorithm to compare protein structures. Procedures to identify structural analogs are typically conducted in three-dimensional space: the tertiary structure of a target protein is matched against each candidate in a database of structures, and goodness of fit is evaluated by a distance-based measure, such as the root-mean-square distance between target and candidate. This is an expensive approach because three-dimensional space is complex. Here, we transform the problem into a simpler one-dimensional procedure. Specifically, we identify and label the 11 most populated residue basins in a database of high-resolution protein structures. Using this 11-letter alphabet, any protein's three-dimensional structure can be transformed into a one-dimensional string by mapping each residue onto its corresponding basin. Similarity between the resultant basin strings can then be evaluated by conventional sequence-based comparison. The disorder → order folding transition is abridged on both sides. At the onset, folding conditions necessitate formation of hydrogen-bonded scaffold elements on which proteins are assembled, severely restricting the magnitude of accessible conformational space. Near the end, chain topology is established prior to emergence of the close-packed native state. At this latter stage of folding, the chain remains molten, and residues populate natural basins that are approximated by the 11 basins derived here. In essence, our algorithm reduces the protein-folding search problem to mapping the amino acid sequence onto a restricted basin string.
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Affiliation(s)
- George D Chellapa
- TC Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, USA
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88
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Huang W, Eichenberger AP, van Gunsteren WF. Molecular dynamics simulation of thionated hen egg white lysozyme. Protein Sci 2012; 21:1153-61. [PMID: 22653637 DOI: 10.1002/pro.2102] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 05/02/2012] [Accepted: 05/23/2012] [Indexed: 11/11/2022]
Abstract
Understanding of the driving forces of protein folding is a complex challenge because different types of interactions play a varying role. To investigate the role of hydrogen bonding involving the backbone, the effect of thio substitutions in a protein, hen egg white lysozyme (HEWL), was investigated through molecular dynamics simulations of native as well as partly (only residues in loops) and fully thionated HEWL using the GROMOS 54A7 force field. The results of the three simulations show that the structural properties of fully thionated HEWL clearly differ from those of the native protein, while for partly thionated HEWL they only changed slightly compared with native HEWL. The analysis of the torsional-angle distributions and hydrogen bonds in the backbone suggests that the α-helical segments of native HEWL tend to show a propensity to convert to 3(10)-helical geometry in fully thionated HEWL. A comparison of the simulated quantities with experimental NMR data such as nuclear overhauser effect (NOE) atom-atom distance bounds and (3)J((H)(N)(H)(α))-couplings measured for native HEWL illustrates that the information content of these quantities with respect to the structural changes induced by thionation of the protein backbone is rather limited.
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Affiliation(s)
- Wei Huang
- Department of Chemistry, Laboratory of Physical Chemistry, Swiss Federal Institute of Technology, Zürich, Switzerland
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89
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Gibrat G, Assairi L, Craescu CT, Hui Bon Hoa G, Loew D, Lombard B, Blouquit L, Bellissent-Funel MC. Use of SANS and biophysical techniques to reveal subtle conformational differences between native apo-calmodulin and its unfolded states. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:1097-106. [PMID: 22709575 DOI: 10.1016/j.bbapap.2012.06.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 05/24/2012] [Accepted: 06/01/2012] [Indexed: 11/16/2022]
Abstract
Apo-calmodulin, a small, mainly α, soluble protein is a calcium-dependent protein activator. It is made of two N- and C-terminal domains having a sequence homology of 70%, an identical folding but different stabilities, and is thus an interesting system for unfolding studies. The use of small angle neutron scattering (SANS) and other biophysical techniques has permitted to reveal conformational difference between native and thermal denatured states of apo-calmodulin. The results show that secondary and tertiary structures of apo-calmodulin evolve in a synchronous way, indicating the absence in the unfolding pathway of molten-globule state sufficiently stable to affect transition curves. From SANS experiments, at 85 °C, apo-calmodulin adopts a polymer chain conformation with some residual local structures. After cooling down, apo-calmodulin recovers a compact state, with a secondary structure close to the native one but with a higher radius of gyration and a different tyrosine environment. In fact on a timescale of few minutes, heat denaturation of apo-calmodulin is partially reversible, but on a time scale of hours (for SANS experiments), the long exposure to heat may lead to a non-reversibility due to some chemical perturbation of the protein. In fact, from Mass Spectrometry measurements, we got evidence of dehydration and deamidation of heated apo-calmodulin.
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90
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Lu WW, Huang RB, Wei YT, Meng JZ, Du LQ, Du QS. Statistical energy potential: reduced representation of Dehouck–Gilis–Rooman function by selecting against decoy datasets. Amino Acids 2012; 42:2353-61. [DOI: 10.1007/s00726-011-0977-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2010] [Accepted: 07/06/2011] [Indexed: 11/24/2022]
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91
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Oladepo SA, Xiong K, Hong Z, Asher SA, Handen J, Lednev IK. UV resonance Raman investigations of peptide and protein structure and dynamics. Chem Rev 2012; 112:2604-28. [PMID: 22335827 PMCID: PMC3349015 DOI: 10.1021/cr200198a] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
| | - Kan Xiong
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Zhenmin Hong
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Sanford A. Asher
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Joseph Handen
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Ave., Albany, NY 12222
| | - Igor K. Lednev
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Ave., Albany, NY 12222
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92
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Rezaei-Ghaleh N, Blackledge M, Zweckstetter M. Intrinsically Disordered Proteins: From Sequence and Conformational Properties toward Drug Discovery. Chembiochem 2012; 13:930-50. [DOI: 10.1002/cbic.201200093] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Indexed: 01/31/2023]
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93
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Held M, Noé F. Calculating kinetics and pathways of protein–ligand association. Eur J Cell Biol 2012; 91:357-64. [DOI: 10.1016/j.ejcb.2011.08.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Revised: 08/08/2011] [Accepted: 08/10/2011] [Indexed: 10/16/2022] Open
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94
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Ma L, Hong Z, Sharma B, Asher S. UV resonance Raman studies of the NaClO4 dependence of poly-L-lysine conformation and hydrogen exchange kinetics. J Phys Chem B 2012; 116:1134-42. [PMID: 22117822 PMCID: PMC3266997 DOI: 10.1021/jp208918n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We used 204 nm excitation UV Resonance Raman (UVRR) spectroscopy to examine the effects of NaClO(4) on the conformation of poly-L-lysine (PLL). The presence of NaClO(4) induces the formation of α-helix, π-helix/bulge, and turn conformations. The dependence of the AmIII(3) frequency on the peptide Ψ Ramachandran angle allows us to experimentally determine the conformational population distributions and the energy landscape of PLL along the Ramachandran Ψ angle. We also used UVRR to measure the NaClO(4) concentration dependence of PLL amide hydrogen exchange kinetics. Exchange rates were determined by fitting the D(2)O exchanging PLL UVRR AmII' band time evolution. Hydrogen exchange is slowed at high NaClO(4) concentrations. The PLL AmII' band exchange kinetics at 0.0, 0.2, and 0.35 M NaClO(4) can be fit by single exponentials, but the AmII' band kinetics of PLL at 0.8 M NaClO(4) requires a double exponential fit. The exchange rates for the extended conformations were monitored by measuring the C(α)-H band kinetics. These kinetics are identical to those of the AmII' band until 0.8 M NaClO(4) whereupon the extended conformation exchange becomes clearly faster than that of the α-helix-like conformations. Our results indicate that ClO(4)(-) binds to the PLL backbone to protect it from OH(-) exchange catalysis. In addition, ClO(4)(-) binding also slows the conformational exchange between the extended and α-helix-like conformations, probably by increasing the activation barriers for conformational interchanges.
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Affiliation(s)
- Lu Ma
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, Tel: (412)-624-8570, Fax: (412)-624-0588
| | - Zhenmin Hong
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, Tel: (412)-624-8570, Fax: (412)-624-0588
| | - Bhavya Sharma
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, Tel: (412)-624-8570, Fax: (412)-624-0588
| | - Sanford Asher
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, Tel: (412)-624-8570, Fax: (412)-624-0588
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95
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Naveed H, Xu Y, Jackups R, Liang J. Predicting three-dimensional structures of transmembrane domains of β-barrel membrane proteins. J Am Chem Soc 2012; 134:1775-81. [PMID: 22148174 DOI: 10.1021/ja209895m] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
β-Barrel membrane proteins are found in the outer membrane of gram-negative bacteria, mitochondria, and chloroplasts. They are important for pore formation, membrane anchoring, and enzyme activity. These proteins are also often responsible for bacterial virulence. Due to difficulties in experimental structure determination, they are sparsely represented in the protein structure databank. We have developed a computational method for predicting structures of the transmembrane (TM) domains of β-barrel membrane proteins. Based on physical principles, our method can predict structures of the TM domain of β-barrel membrane proteins of novel topology, including those from eukaryotic mitochondria. Our method is based on a model of physical interactions, a discrete conformational state space, an empirical potential function, as well as a model to account for interstrand loop entropy. We are able to construct three-dimensional atomic structure of the TM domains from sequences for a set of 23 nonhomologous proteins (resolution 1.8-3.0 Å). The median rmsd of TM domains containing 75-222 residues between predicted and measured structures is 3.9 Å for main chain atoms. In addition, stability determinants and protein-protein interaction sites can be predicted. Such predictions on eukaryotic mitochondria outer membrane protein Tom40 and VDAC are confirmed by independent mutagenesis and chemical cross-linking studies. These results suggest that our model captures key components of the organization principles of β-barrel membrane protein assembly.
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Affiliation(s)
- Hammad Naveed
- Department of Bioengineering, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, Illinois 60607, USA
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96
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97
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Nussinov R, Tsai CJ. The different ways through which specificity works in orthosteric and allosteric drugs. Curr Pharm Des 2012; 18:1311-6. [PMID: 22316155 PMCID: PMC7458136 DOI: 10.2174/138161212799436377] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 12/06/2011] [Indexed: 11/22/2022]
Abstract
Currently, there are two types of drugs on the market: orthosteric, which bind at the active site; and allosteric, which bind elsewhere on the protein surface, and allosterically change the conformation of the protein binding site. In this perspective we argue that the different mechanisms through which the two drug types affect protein activity and their potential pitfalls call for different considerations in drug design. The key problem facing orthosteric drugs is side effects which can occur by drug binding to homologous proteins sharing a similar binding site. Hence, orthosteric drugs should have very high affinity to the target; this would allow a low dosage to selectively achieve the goal of target-only binding. By contrast, allosteric drugs work by shifting the free energy landscape. Their binding to the protein surface perturbs the protein surface atoms, and the perturbation propagates like waves, finally reaching the binding site. Effective drugs should have atoms in good contact with the 'right' protein atoms; that is, the contacts should elicit propagation waves optimally reaching the protein binding site target. While affinity is important, the design should consider the protein conformational ensemble and the preferred propagation states. We provide examples from functional in vivo scenarios for both types of cases, and suggest how high potency can be achieved in allosteric drug development.
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98
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Wang J, Lu H, Ren Y, Zhang Y, Morton M, Cheng J, Lin Y. Interrupted Helical Structure of Grafted Polypeptides in Brush-Like Macromolecules. Macromolecules 2011. [DOI: 10.1021/ma201833b] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Jing Wang
- Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Hua Lu
- Department of Materials Science and Engineering, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Yuan Ren
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Yanfeng Zhang
- Department of Materials Science and Engineering, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Martha Morton
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Jianjun Cheng
- Department of Materials Science and Engineering, University of Illinois at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Yao Lin
- Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, United States
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
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99
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Leelananda SP, Towfic F, Jernigan RL, Kloczkowski A. Exploration of the relationship between topology and designability of conformations. J Chem Phys 2011; 134:235101. [PMID: 21702580 DOI: 10.1063/1.3596947] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Protein structures are evolutionarily more conserved than sequences, and sequences with very low sequence identity frequently share the same fold. This leads to the concept of protein designability. Some folds are more designable and lots of sequences can assume that fold. Elucidating the relationship between protein sequence and the three-dimensional (3D) structure that the sequence folds into is an important problem in computational structural biology. Lattice models have been utilized in numerous studies to model protein folds and predict the designability of certain folds. In this study, all possible compact conformations within a set of two-dimensional and 3D lattice spaces are explored. Complementary interaction graphs are then generated for each conformation and are described using a set of graph features. The full HP sequence space for each lattice model is generated and contact energies are calculated by threading each sequence onto all the possible conformations. Unique conformation giving minimum energy is identified for each sequence and the number of sequences folding to each conformation (designability) is obtained. Machine learning algorithms are used to predict the designability of each conformation. We find that the highly designable structures can be distinguished from other non-designable conformations based on certain graphical geometric features of the interactions. This finding confirms the fact that the topology of a conformation is an important determinant of the extent of its designability and suggests that the interactions themselves are important for determining the designability.
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Affiliation(s)
- Sumudu P Leelananda
- L. H. Baker Center for Bioinformatics and Biological Statistics, Iowa State University, Ames, Iowa 50010, USA
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100
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Abstract
How is specificity transmitted over long distances at the molecular level? REs (regulatory elements) are often far from transcription start sites. In the present review we discuss possible mechanisms to explain how information from specific REs is conveyed to the basal transcription machinery through TFs (transcription factors) and the Mediator complex. We hypothesize that this occurs through allosteric pathways: binding of a TF to a RE results in changes in the AD (activation domain) of the TF, which binds to Mediator and alters the distribution of the Mediator conformations, thereby affecting transcription initiation/activation. We argue that Mediator is formed by highly disordered proteins with large densely packed interfaces that make efficient long-range signal propagation possible. We suggest two possible general mechanisms for Mediator action: one in which Mediator influences PIC (pre-initiation complex) assembly and transcription initiation, and another in which Mediator exerts its effect on the already assembled but stalled transcription complex. We summarize (i) relevant information from the literature about Mediator composition, organization and structure; (ii) Mediator interaction partners and their effect on Mediator conformation, function and correlation to the RNA Pol II (polymerase II) CTD (C-terminal domain) phosphorylation; and (iii) propose that different allosteric signal propagation pathways in Mediator relate to PIC assembly and polymerase activation of the stalled transcription complex. The emerging picture provides for the first time a mechanistic view of allosteric signalling from the RE sequence to transcription activation, and an insight into how gene specificity and signal transmission can take place in transcription initiation.
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Affiliation(s)
- Chung-Jung Tsai
- Basic Science Program, SAIC-Frederick, Center for Cancer Research Nanobiology Program NCI-Frederick, Frederick, MD 21702, U.S.A
| | - Ruth Nussinov
- Basic Science Program, SAIC-Frederick, Center for Cancer Research Nanobiology Program NCI-Frederick, Frederick, MD 21702, U.S.A
- Sackler Institute of Molecular Medicine, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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