1
|
Parves MR, Solares MJ, Dearnaley WJ, Kelly DF. Elucidating structural variability in p53 conformers using combinatorial refinement strategies and molecular dynamics. Cancer Biol Ther 2024; 25:2290732. [PMID: 38073067 PMCID: PMC10732606 DOI: 10.1080/15384047.2023.2290732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 11/29/2023] [Indexed: 12/18/2023] Open
Abstract
Low molecular weight proteins and protein assemblies can now be investigated using cryo-electron microscopy (EM) as a complement to traditional structural biology techniques. It is important, however, to not lose sight of the dynamic information inherent in macromolecules that give rise to their exquisite functionality. As computational methods continue to advance the field of biomedical imaging, so must strategies to resolve the minute details of disease-related entities. Here, we employed combinatorial modeling approaches to assess flexible properties among low molecular weight proteins (~100 kDa or less). Through a blend of rigid body refinement and simulated annealing, we determined new hidden conformations for wild type p53 monomer and dimer forms. Structures for both states converged to yield new conformers, each revealing good stereochemistry and dynamic information about the protein. Based on these insights, we identified fluid parts of p53 that complement the stable central core of the protein responsible for engaging DNA. Molecular dynamics simulations corroborated the modeling results and helped pinpoint the more flexible residues in wild type p53. Overall, the new computational methods may be used to shed light on other small protein features in a vast ensemble of structural data that cannot be easily delineated by other algorithms.
Collapse
Affiliation(s)
- Md Rimon Parves
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA, USA
- Biochemistry, Microbiology, and Molecular Biology Graduate Program, Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
| | - Maria J. Solares
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA, USA
- Molecular, Cellular, and Integrative Biosciences Graduate Program, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, USA
| | - William J. Dearnaley
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA, USA
| | - Deborah F. Kelly
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA, USA
| |
Collapse
|
2
|
Pang YT, Yang L, Gumbart JC. From simple to complex: Reconstructing all-atom structures from coarse-grained models using cg2all. Structure 2024; 32:5-7. [PMID: 38181727 PMCID: PMC11283325 DOI: 10.1016/j.str.2023.12.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 12/08/2023] [Accepted: 12/08/2023] [Indexed: 01/07/2024]
Abstract
In this issue of Structure, Heo and Feig present cg2all, a novel deep-learning model capable of efficiently predicting all-atom protein structures from coarse-grained (CG) representations. The model maintains high accuracy, even when the CG model is simplified to a single bead per residue, and has a number of promising applications.
Collapse
Affiliation(s)
- Yui Tik Pang
- School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Lixinhao Yang
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - James C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA; School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA.
| |
Collapse
|
3
|
Kelly DF, Jonaid GM, Kaylor L, Solares MJ, Berry S, DiCecco LA, Dearnaley W, Casasanta M. Delineating Conformational Variability in Small Protein Structures Using Combinatorial Refinement Strategies. MICROMACHINES 2023; 14:1869. [PMID: 37893306 PMCID: PMC10609307 DOI: 10.3390/mi14101869] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 09/22/2023] [Accepted: 09/27/2023] [Indexed: 10/29/2023]
Abstract
As small protein assemblies and even small proteins are becoming more amenable to cryo-Electron Microscopy (EM) structural studies, it is important to consider the complementary dynamic information present in the data. Current computational strategies are limited in their ability to resolve minute differences among low molecular weight entities. Here, we demonstrate a new combinatorial approach to delineate flexible conformations among small proteins using real-space refinement applications. We performed a meta-analysis of structural data for the SARS CoV-2 Nucleocapsid (N) protein using a combination of rigid-body refinement and simulated annealing methods. For the N protein monomer, we determined three new flexible conformers with good stereochemistry and quantitative comparisons provided new evidence of their dynamic properties. A similar analysis performed for the N protein dimer showed only minor structural differences among the flexible models. These results suggested a more stable view of the N protein dimer than the monomer structure. Taken together, the new computational strategies can delineate conformational changes in low molecular weight proteins that may go unnoticed by conventional assessments. The results also suggest that small proteins may be further stabilized for structural studies through the use of solution components that limit the movement of external flexible regions.
Collapse
Affiliation(s)
- Deborah F. Kelly
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA 16802, USA
| | - G M Jonaid
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA 16802, USA
- Bioinformatics and Genomics Graduate Program, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Liam Kaylor
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA 16802, USA
- Molecular, Cellular, and Integrative Biosciences Graduate Program, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Maria J. Solares
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA 16802, USA
- Molecular, Cellular, and Integrative Biosciences Graduate Program, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Samantha Berry
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA 16802, USA
| | - Liza-Anastasia DiCecco
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA 16802, USA
| | - William Dearnaley
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA 16802, USA
| | - Michael Casasanta
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
- Center for Structural Oncology, Pennsylvania State University, University Park, PA 16802, USA
| |
Collapse
|
4
|
Selvaraj C, Rudhra O, Alothaim AS, Alkhanani M, Singh SK. Structure and chemistry of enzymatic active sites that play a role in the switch and conformation mechanism. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2022; 130:59-83. [PMID: 35534116 DOI: 10.1016/bs.apcsb.2022.02.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Enzymes, which are biological molecules, are constructed from polypeptide chains, and these molecules are activated through reaction mechanisms. It is the role of enzymes to speed up chemical reactions that are used to build or break down cell structures. Activation energy is reduced by the enzymes' selective binding of substrates in a protected environment. In enzyme tertiary structures, the active sites are commonly situated in a "cleft," which necessitates the diffusion of substrates and products. The amino acid residues of the active site may be far apart in the primary structure owing to the folding required for tertiary structure. Due to their critical role in substrate binding and attraction, changes in amino acid structure at or near the enzyme's active site usually alter enzyme activity. At the enzyme's active site, or where the chemical reactions occur, the substrate is bound. Enzyme substrates are the primary targets of the enzyme's active site, which is designed to assist in the chemical reaction. This chapter elucidates the summary of structure and chemistry of enzymes, their active site features, charges and role of water in the structures to clarify the biochemistry of the enzymes in the depth of atomic features.
Collapse
Affiliation(s)
- Chandrabose Selvaraj
- Computer Aided Drug Design and Molecular Modelling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India.
| | - Ondipilliraja Rudhra
- Computer Aided Drug Design and Molecular Modelling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India
| | - Abdulaziz S Alothaim
- Department of Biology, College of Science in Zulfi, Majmaah University, Majmaah, Saudi Arabia
| | - Mustfa Alkhanani
- Emergency Service Department, College of Applied Sciences, Al Maarefa University, Riyadh, Saudi Arabia
| | - Sanjeev Kumar Singh
- Computer Aided Drug Design and Molecular Modelling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India.
| |
Collapse
|
5
|
Refinement of a cryo-EM structure of hERG: Bridging structure and function. Biophys J 2021; 120:738-748. [PMID: 33476597 DOI: 10.1016/j.bpj.2021.01.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 12/22/2020] [Accepted: 01/11/2021] [Indexed: 01/16/2023] Open
Abstract
The human-ether-a-go-go-related gene (hERG) encodes the voltage-gated potassium channel (KCNH2 or Kv11.1, commonly known as hERG). This channel plays a pivotal role in the stability of phase 3 repolarization of the cardiac action potential. Although a high-resolution cryo-EM structure is available for its depolarized (open) state, the structure surprisingly did not feature many functionally important interactions established by previous biochemical and electrophysiology experiments. Using molecular dynamics flexible fitting (MDFF), we refined the structure and recovered the missing functionally relevant salt bridges in hERG in its depolarized state. We also performed electrophysiology experiments to confirm the functional relevance of a novel salt bridge predicted by our refinement protocol. Our work shows how refinement of a high-resolution cryo-EM structure helps to bridge the existing gap between the structure and function in the voltage-sensing domain (VSD) of hERG.
Collapse
|
6
|
Phillips JC, Hardy DJ, Maia JDC, Stone JE, Ribeiro JV, Bernardi RC, Buch R, Fiorin G, Hénin J, Jiang W, McGreevy R, Melo MCR, Radak BK, Skeel RD, Singharoy A, Wang Y, Roux B, Aksimentiev A, Luthey-Schulten Z, Kalé LV, Schulten K, Chipot C, Tajkhorshid E. Scalable molecular dynamics on CPU and GPU architectures with NAMD. J Chem Phys 2020; 153:044130. [PMID: 32752662 PMCID: PMC7395834 DOI: 10.1063/5.0014475] [Citation(s) in RCA: 1392] [Impact Index Per Article: 348.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 07/01/2020] [Indexed: 02/06/2023] Open
Abstract
NAMDis a molecular dynamics program designed for high-performance simulations of very large biological objects on CPU- and GPU-based architectures. NAMD offers scalable performance on petascale parallel supercomputers consisting of hundreds of thousands of cores, as well as on inexpensive commodity clusters commonly found in academic environments. It is written in C++ and leans on Charm++ parallel objects for optimal performance on low-latency architectures. NAMD is a versatile, multipurpose code that gathers state-of-the-art algorithms to carry out simulations in apt thermodynamic ensembles, using the widely popular CHARMM, AMBER, OPLS, and GROMOS biomolecular force fields. Here, we review the main features of NAMD that allow both equilibrium and enhanced-sampling molecular dynamics simulations with numerical efficiency. We describe the underlying concepts utilized by NAMD and their implementation, most notably for handling long-range electrostatics; controlling the temperature, pressure, and pH; applying external potentials on tailored grids; leveraging massively parallel resources in multiple-copy simulations; and hybrid quantum-mechanical/molecular-mechanical descriptions. We detail the variety of options offered by NAMD for enhanced-sampling simulations aimed at determining free-energy differences of either alchemical or geometrical transformations and outline their applicability to specific problems. Last, we discuss the roadmap for the development of NAMD and our current efforts toward achieving optimal performance on GPU-based architectures, for pushing back the limitations that have prevented biologically realistic billion-atom objects to be fruitfully simulated, and for making large-scale simulations less expensive and easier to set up, run, and analyze. NAMD is distributed free of charge with its source code at www.ks.uiuc.edu.
Collapse
Affiliation(s)
| | - David J. Hardy
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Julio D. C. Maia
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | - John E. Stone
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | - João V. Ribeiro
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Rafael C. Bernardi
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | | | - Giacomo Fiorin
- National Heart, Lung and Blood Institute, National
Institutes of Health, Bethesda, Maryland 20814,
USA
| | - Jérôme Hénin
- Laboratoire de Biochimie Théorique UPR 9080, CNRS
and Université de Paris, Paris, France
| | | | - Ryan McGreevy
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | | | - Brian K. Radak
- NIH Center for Macromolecular Modeling and
Bioinformatics, Theoretical and Computational Biophysics Group, Beckman Institute for
Advanced Science and Technology, University of Illinois at
Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Robert D. Skeel
- School of Mathematical and Statistical Sciences,
Arizona State University, Tempe, Arizona 85281,
USA
| | - Abhishek Singharoy
- School of Molecular Sciences, Arizona State
University, Tempe, Arizona 85281, USA
| | - Yi Wang
- Department of Physics, The Chinese University of
Hong Kong, Shatin, Hong Kong, China
| | - Benoît Roux
- Department of Biochemistry, University of
Chicago, Chicago, Illinois 60637, USA
| | | | | | | | | | - Christophe Chipot
- Authors to whom correspondence should be addressed:
and . URL: http://www.ks.uiuc.edu
| | - Emad Tajkhorshid
- Authors to whom correspondence should be addressed:
and . URL: http://www.ks.uiuc.edu
| |
Collapse
|
7
|
Dodd T, Yan C, Ivanov I. Simulation-Based Methods for Model Building and Refinement in Cryoelectron Microscopy. J Chem Inf Model 2020; 60:2470-2483. [PMID: 32202798 DOI: 10.1021/acs.jcim.0c00087] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Advances in cryoelectron microscopy (cryo-EM) have revolutionized the structural investigation of large macromolecular assemblies. In this review, we first provide a broad overview of modeling methods used for flexible fitting of molecular models into cryo-EM density maps. We give special attention to approaches rooted in molecular simulations-atomistic molecular dynamics and Monte Carlo. Concise descriptions of the methods are given along with discussion of their advantages, limitations, and most popular alternatives. We also describe recent extensions of the widely used molecular dynamics flexible fitting (MDFF) method and discuss how different model-building techniques could be incorporated into new hybrid modeling schemes and simulation workflows. Finally, we provide two illustrative examples of model-building and refinement strategies employing MDFF, cascade MDFF, and RosettaCM. These examples come from recent cryo-EM studies that elucidated transcription preinitiation complexes and shed light on the functional roles of these assemblies in gene expression and gene regulation.
Collapse
Affiliation(s)
- Thomas Dodd
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States.,Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30302, United States
| | - Chunli Yan
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States.,Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30302, United States
| | - Ivaylo Ivanov
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States.,Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30302, United States
| |
Collapse
|
8
|
Pintilie G, Zhang K, Su Z, Li S, Schmid MF, Chiu W. Measurement of atom resolvability in cryo-EM maps with Q-scores. Nat Methods 2020; 17:328-334. [PMID: 32042190 PMCID: PMC7446556 DOI: 10.1038/s41592-020-0731-1] [Citation(s) in RCA: 206] [Impact Index Per Article: 51.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 12/31/2019] [Indexed: 01/18/2023]
Abstract
Cryogenic electron microscopy (cryo-EM) maps are now at the point where resolvability of individual atoms can be achieved. However, resolvability is not necessarily uniform throughout the map. We introduce a quantitative parameter to characterize the resolvability of individual atoms in cryo-EM maps, the map Q-score. Q-scores can be calculated for atoms in proteins, nucleic acids, water, ligands and other solvent atoms, using models fitted to or derived from cryo-EM maps. Q-scores can also be averaged to represent larger features such as entire residues and nucleotides. Averaged over entire models, Q-scores correlate very well with the estimated resolution of cryo-EM maps for both protein and RNA. Assuming the models they are calculated from are well fitted to the map, Q-scores can be used as a measure of resolvability in cryo-EM maps at various scales, from entire macromolecules down to individual atoms. Q-score analysis of multiple cryo-EM maps of the same proteins derived from different laboratories confirms the reproducibility of structural features from side chains down to water and ion atoms.
Collapse
Affiliation(s)
- Grigore Pintilie
- Department of Bioengineering, James H. Clark Center, Stanford University, Stanford, CA, USA.
| | - Kaiming Zhang
- Department of Bioengineering, James H. Clark Center, Stanford University, Stanford, CA, USA
| | - Zhaoming Su
- Department of Bioengineering, James H. Clark Center, Stanford University, Stanford, CA, USA
| | - Shanshan Li
- Department of Bioengineering, James H. Clark Center, Stanford University, Stanford, CA, USA
| | - Michael F Schmid
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, USA
| | - Wah Chiu
- Department of Bioengineering, James H. Clark Center, Stanford University, Stanford, CA, USA.
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, USA.
| |
Collapse
|
9
|
Capsid expansion of bacteriophage T5 revealed by high resolution cryoelectron microscopy. Proc Natl Acad Sci U S A 2019; 116:21037-21046. [PMID: 31578255 DOI: 10.1073/pnas.1909645116] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The large (90-nm) icosahedral capsid of bacteriophage T5 is composed of 775 copies of the major capsid protein (mcp) together with portal, protease, and decoration proteins. Its assembly is a regulated process that involves several intermediates, including a thick-walled round precursor prohead that expands as the viral DNA is packaged to yield a thin-walled and angular mature capsid. We investigated capsid maturation by comparing cryoelectron microscopy (cryo-EM) structures of the prohead, the empty expanded capsid both with and without decoration protein, and the virion capsid at a resolution of 3.8 Å for the latter. We detail the molecular structure of the mcp, its complex pattern of interactions, and their evolution during maturation. The bacteriophage T5 mcp is a variant of the canonical HK97-fold with a high level of plasticity that allows for the precise assembly of a giant macromolecule and the adaptability needed to interact with other proteins and the packaged DNA.
Collapse
|
10
|
Seffernick J, Harvey SR, Wysocki VH, Lindert S. Predicting Protein Complex Structure from Surface-Induced Dissociation Mass Spectrometry Data. ACS CENTRAL SCIENCE 2019; 5:1330-1341. [PMID: 31482115 PMCID: PMC6716128 DOI: 10.1021/acscentsci.8b00912] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Indexed: 05/23/2023]
Abstract
Recently, mass spectrometry (MS) has become a viable method for elucidation of protein structure. Surface-induced dissociation (SID), colliding multiply charged protein complexes or other ions with a surface, has been paired with native MS to provide useful structural information such as connectivity and topology for many different protein complexes. We recently showed that SID gives information not only on connectivity and topology but also on relative interface strengths. However, SID has not yet been coupled with computational structure prediction methods that could use the sparse information from SID to improve the prediction of quaternary structures, i.e., how protein subunits interact with each other to form complexes. Protein-protein docking, a computational method to predict the quaternary structure of protein complexes, can be used in combination with subunit structures from X-ray crystallography and NMR in situations where it is difficult to obtain an experimental structure of an entire complex. While de novo structure prediction can be successful, many studies have shown that inclusion of experimental data can greatly increase prediction accuracy. In this study, we show that the appearance energy (AE, defined as 10% fragmentation) extracted from SID can be used in combination with Rosetta to successfully evaluate protein-protein docking poses. We developed an improved model to predict measured SID AEs and incorporated this model into a scoring function that combines the RosettaDock scoring function with a novel SID scoring term, which quantifies agreement between experiments and structures generated from RosettaDock. As a proof of principle, we tested the effectiveness of these restraints on 57 systems using ideal SID AE data (AE determined from crystal structures using the predictive model). When theoretical AEs were used, the RMSD of the selected structure improved or stayed the same in 95% of cases. When experimental SID data were incorporated on a different set of systems, the method predicted near-native structures (less than 2 Å root-mean-square deviation, RMSD, from native) for 6/9 tested cases, while unrestrained RosettaDock (without SID data) only predicted 3/9 such cases. Score versus RMSD funnel profiles were also improved when SID data were included. Additionally, we developed a confidence measure to evaluate predicted model quality in the absence of a crystal structure.
Collapse
|
11
|
Strickland KM, Stock G, Cui G, Hwang H, Infield DT, Schmidt-Krey I, McCarty NA, Gumbart JC. ATP-Dependent Signaling in Simulations of a Revised Model of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). J Phys Chem B 2019; 123:3177-3188. [PMID: 30921517 DOI: 10.1021/acs.jpcb.8b11970] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) is a member of the ATP-binding cassette (ABC) transporter superfamily that has uniquely evolved to function as a chloride channel. It binds and hydrolyzes ATP at its nucleotide binding domains to form a pore providing a diffusive pathway within its transmembrane domains. CFTR is the only known protein from the ABC superfamily with channel activity, and its dysfunction causes the disease cystic fibrosis. While much is known about the functional aspects of CFTR, significant gaps remain, such as the structure-function relationship underlying signaling of ATP binding. In the present work, we refined an existing homology model using an intermediate-resolution (9 Å) published cryo-electron microscopy map. The newly derived models have been simulated in equilibrium molecular dynamics simulations for a total of 2.5 μs in multiple ATP-occupancy states. Putative conformational movements connecting ATP binding with pore formation are elucidated and quantified. Additionally, new interdomain interactions between E543, K968, and K1292 have been identified and confirmed experimentally; these interactions may be relevant for signaling ATP binding and hydrolysis to the transmembrane domains and induction of pore opening.
Collapse
Affiliation(s)
- Kerry M Strickland
- School of Chemistry and Biochemistry , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| | - Gorman Stock
- School of Chemistry and Biochemistry , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| | - Guiying Cui
- Division of Pulmonology, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center , Emory University School of Medicine and Children's Healthcare of Atlanta , Atlanta , Georgia 30322 , United States
| | - Hyea Hwang
- School of Materials Science and Engineering , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| | - Daniel T Infield
- Division of Pulmonology, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center , Emory University School of Medicine and Children's Healthcare of Atlanta , Atlanta , Georgia 30322 , United States
| | - Ingeborg Schmidt-Krey
- School of Chemistry and Biochemistry , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States.,School of Biological Sciences , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States.,Parker H. Petit Institute for Bioengineering and Bioscience , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| | - Nael A McCarty
- Division of Pulmonology, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center , Emory University School of Medicine and Children's Healthcare of Atlanta , Atlanta , Georgia 30322 , United States.,Parker H. Petit Institute for Bioengineering and Bioscience , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| | - James C Gumbart
- School of Chemistry and Biochemistry , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States.,School of Biological Sciences , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States.,Parker H. Petit Institute for Bioengineering and Bioscience , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States.,School of Physics , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| |
Collapse
|
12
|
Wang Y, Shekhar M, Thifault D, Williams CJ, McGreevy R, Richardson J, Singharoy A, Tajkhorshid E. Constructing atomic structural models into cryo-EM densities using molecular dynamics - Pros and cons. J Struct Biol 2018; 204:319-328. [PMID: 30092279 PMCID: PMC6394829 DOI: 10.1016/j.jsb.2018.08.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 07/31/2018] [Accepted: 08/05/2018] [Indexed: 01/11/2023]
Abstract
Accurate structure determination from electron density maps at 3-5 Å resolution necessitates a balance between extensive global and local sampling of atomistic models, yet with the stereochemical correctness of backbone and sidechain geometries. Molecular Dynamics Flexible Fitting (MDFF), particularly through a resolution-exchange scheme, ReMDFF, provides a robust way of achieving this balance for hybrid structure determination. Employing two high-resolution density maps, namely that of β-galactosidase at 3.2 Å and TRPV1 at 3.4 Å, we showcase the quality of ReMDFF-generated models, comparing them against ones submitted by independent research groups for the 2015-2016 Cryo-EM Model Challenge. This comparison offers a clear evaluation of ReMDFF's strengths and shortcomings, and those of data-guided real-space refinements in general. ReMDFF results scored highly on the various metric for judging the quality-of-fit and quality-of-model. However, some systematic discrepancies are also noted employing a Molprobity analysis, that are reproducible across multiple competition entries. A space of key refinement parameters is explored within ReMDFF to observe their impact within the final model. Choice of force field parameters and initial model seem to have the most significant impact on ReMDFF model-quality. To this end, very recently developed CHARMM36m force field parameters provide now more refined ReMDFF models than the ones originally submitted to the Cryo-EM challenge. Finally, a set of good-practices is prescribed for the community to benefit from the MDFF developments.
Collapse
Affiliation(s)
- Yuhang Wang
- Center for Biophysics and Quantitative Biology, College of Medicine, Department of Biochemistry, Beckman Institute for Advanced Science and Technology, and University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Mrinal Shekhar
- Center for Biophysics and Quantitative Biology, College of Medicine, Department of Biochemistry, Beckman Institute for Advanced Science and Technology, and University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Darren Thifault
- School of Molecular Sciences, Center for Applied Structural Discovery, Arizona State University, Tempe, AZ 85287, United States
| | | | - Ryan McGreevy
- Center for Biophysics and Quantitative Biology, College of Medicine, Department of Biochemistry, Beckman Institute for Advanced Science and Technology, and University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Jane Richardson
- Department of Biochemistry, Duke University, Durham, NC 27710, United States
| | - Abhishek Singharoy
- School of Molecular Sciences, Center for Applied Structural Discovery, Arizona State University, Tempe, AZ 85287, United States.
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| |
Collapse
|
13
|
Tekpinar M. Flexible fitting to cryo-electron microscopy maps with coarse-grained elastic network models. MOLECULAR SIMULATION 2018. [DOI: 10.1080/08927022.2018.1431835] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
14
|
Alvarez FJD, He S, Perilla JR, Jang S, Schulten K, Engelman AN, Scheres SHW, Zhang P. CryoEM structure of MxB reveals a novel oligomerization interface critical for HIV restriction. SCIENCE ADVANCES 2017; 3:e1701264. [PMID: 28929138 PMCID: PMC5600524 DOI: 10.1126/sciadv.1701264] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Accepted: 08/17/2017] [Indexed: 06/01/2023]
Abstract
Human dynamin-like, interferon-induced myxovirus resistance 2 (Mx2 or MxB) is a potent HIV-1 inhibitor. Antiviral activity requires both the amino-terminal region of MxB and protein oligomerization, each of which has eluded structural determination due to difficulties in protein preparation. We report that maltose binding protein-fused, full-length wild-type MxB purifies as oligomers and further self-assembles into helical arrays in physiological salt. Guanosine triphosphate (GTP), but not guanosine diphosphate, binding results in array disassembly, whereas subsequent GTP hydrolysis allows its reformation. Using cryo-electron microscopy (cryoEM), we determined the MxB assembly structure at 4.6 Å resolution, representing the first near-atomic resolution structure in the mammalian dynamin superfamily. The structure revealed previously described and novel MxB assembly interfaces. Mutational analyses demonstrated a critical role for one of the novel interfaces in HIV-1 restriction.
Collapse
Affiliation(s)
- Frances J. D. Alvarez
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
| | - Shaoda He
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Juan R. Perilla
- Department of Physics and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Sooin Jang
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
| | - Klaus Schulten
- Department of Physics and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Alan N. Engelman
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
| | - Sjors H. W. Scheres
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Peijun Zhang
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
- Division of Structural Biology, Henry Wellcome Building for Genomic Medicine, University of Oxford, Headington, Oxford OX3 7BN, UK
- Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
| |
Collapse
|
15
|
The C-Terminal Arm of the Human Papillomavirus Major Capsid Protein Is Immunogenic and Involved in Virus-Host Interaction. Structure 2017; 24:874-85. [PMID: 27276427 DOI: 10.1016/j.str.2016.04.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 04/09/2016] [Accepted: 04/11/2016] [Indexed: 01/22/2023]
Abstract
Cervical cancer is the second most prevalent malignant tumor among women worldwide. High-risk human papillomaviruses (HPVs) are believed to be the major causative pathogens of mucosal epithelial cancers including cervical cancer. The HPV capsid is made up of 360 copies of major (L1) and 72 copies of minor (L2) capsid proteins. To date, limited high-resolution structural information about the HPV capsid has hindered attempts to understand details concerning the mechanisms by which HPV assembles and infects cells. In this study, we have constructed a pseudo-atomic model of the HPV59 L1-only capsid and demonstrate that the C-terminal arm of L1 participates in virus-host interactions. Moreover, when conjugated to a scaffold protein, keyhole limpet hemocyanin (KLH), this arm is immunogenic in vivo. These results provide new insights that will help elucidate HPV biology, and hence pave a way for the design of next-generation HPV vaccines.
Collapse
|
16
|
Singharoy A, Teo I, McGreevy R, Stone JE, Zhao J, Schulten K. Molecular dynamics-based refinement and validation for sub-5 Å cryo-electron microscopy maps. eLife 2016; 5. [PMID: 27383269 PMCID: PMC4990421 DOI: 10.7554/elife.16105] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 07/06/2016] [Indexed: 12/12/2022] Open
Abstract
Two structure determination methods, based on the molecular dynamics flexible fitting (MDFF) paradigm, are presented that resolve sub-5 Å cryo-electron microscopy (EM) maps with either single structures or ensembles of such structures. The methods, denoted cascade MDFF and resolution exchange MDFF, sequentially re-refine a search model against a series of maps of progressively higher resolutions, which ends with the original experimental resolution. Application of sequential re-refinement enables MDFF to achieve a radius of convergence of ~25 Å demonstrated with the accurate modeling of β-galactosidase and TRPV1 proteins at 3.2 Å and 3.4 Å resolution, respectively. The MDFF refinements uniquely offer map-model validation and B-factor determination criteria based on the inherent dynamics of the macromolecules studied, captured by means of local root mean square fluctuations. The MDFF tools described are available to researchers through an easy-to-use and cost-effective cloud computing resource on Amazon Web Services. DOI:http://dx.doi.org/10.7554/eLife.16105.001 To understand the roles that proteins and other large molecules play inside cells, it is important to determine their structures. One of the techniques that researchers can use to do this is called cryo-electron microscopy (cryo-EM), which rapidly freezes molecules to fix them in position before imaging them in fine detail. The cryo-EM images are like maps that show the approximate position of atoms. These images must then be processed in order to build a three-dimensional model of the protein that shows how its atoms are arranged relative to each other. One computational approach called Molecular Dynamics Flexible Fitting (MDFF) works by flexibly fitting possible atomic structures into cryo-EM maps. Although this approach works well with relatively undetailed (or ‘low resolution’) cryo-EM images, it struggles to handle the high-resolution cryo-EM maps now being generated. Singharoy, Teo, McGreevy et al. have now developed two MDFF methods – called cascade MDFF and resolution exchange MDFF – that help to resolve atomic models of biological molecules from cryo-EM images. Each method can refine poorly guessed models into ones that are consistent with the high-resolution experimental images. The refinement is achieved by interpreting a range of images that starts with a ‘fuzzy’ image. The contrast of the image is then progressively improved until an image is produced that has a resolution that is good enough to almost distinguish individual atoms. The method works because each cryo-EM image shows not just one, but a collection of atomic structures that the molecule can take on, with the fuzzier parts of the image representing the more flexible parts of the molecule. By taking into account this flexibility, the large-scale features of the protein structure can be determined first from the fuzzier images, and increasing the contrast of the images allows smaller-scale refinements to be made to the structure. The MDFF tools have been designed to be easy to use and are available to researchers at low cost through cloud computing platforms. They can now be used to unravel the structure of many different proteins and protein complexes including those involved in photosynthesis, respiration and protein synthesis. DOI:http://dx.doi.org/10.7554/eLife.16105.002
Collapse
Affiliation(s)
- Abhishek Singharoy
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States
| | - Ivan Teo
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States.,Department of Physics, University of Illinois at Urbana-Champaign, Urbana, United States
| | - Ryan McGreevy
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States
| | - John E Stone
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States
| | - Jianhua Zhao
- Department of Biochemistry and Biophysics, University of California San Francisco School of Medicine, San Francisco, United States
| | - Klaus Schulten
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States.,Department of Physics, University of Illinois at Urbana-Champaign, Urbana, United States
| |
Collapse
|
17
|
Lindert S, McCammon JA. Improved cryoEM-Guided Iterative Molecular Dynamics--Rosetta Protein Structure Refinement Protocol for High Precision Protein Structure Prediction. J Chem Theory Comput 2016; 11:1337-46. [PMID: 25883538 PMCID: PMC4393324 DOI: 10.1021/ct500995d] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Indexed: 12/13/2022]
Abstract
![]()
Many excellent methods exist that
incorporate cryo-electron microscopy
(cryoEM) data to constrain computational protein structure prediction
and refinement. Previously, it was shown that iteration of two such
orthogonal sampling and scoring methods – Rosetta and molecular
dynamics (MD) simulations – facilitated exploration of conformational
space in principle. Here, we go beyond a proof-of-concept study and
address significant remaining limitations of the iterative MD–Rosetta
protein structure refinement protocol. Specifically, all parts of
the iterative refinement protocol are now guided by medium-resolution
cryoEM density maps, and previous knowledge about the native structure
of the protein is no longer necessary. Models are identified solely
based on score or simulation time. All four benchmark proteins showed
substantial improvement through three rounds of the iterative refinement
protocol. The best-scoring final models of two proteins had sub-Ångstrom
RMSD to the native structure over residues in secondary structure
elements. Molecular dynamics was most efficient in refining secondary
structure elements and was thus highly complementary to the Rosetta
refinement which is most powerful in refining side chains and loop
regions.
Collapse
|
18
|
Xu X, Yan C, Wohlhueter R, Ivanov I. Integrative Modeling of Macromolecular Assemblies from Low to Near-Atomic Resolution. Comput Struct Biotechnol J 2015; 13:492-503. [PMID: 26557958 PMCID: PMC4588362 DOI: 10.1016/j.csbj.2015.08.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/09/2015] [Accepted: 08/13/2015] [Indexed: 02/02/2023] Open
Abstract
While conventional high-resolution techniques in structural biology are challenged by the size and flexibility of many biological assemblies, recent advances in low-resolution techniques such as cryo-electron microscopy (cryo-EM) and small angle X-ray scattering (SAXS) have opened up new avenues to define the structures of such assemblies. By systematically combining various sources of structural, biochemical and biophysical information, integrative modeling approaches aim to provide a unified structural description of such assemblies, starting from high-resolution structures of the individual components and integrating all available information from low-resolution experimental methods. In this review, we describe integrative modeling approaches, which use complementary data from either cryo-EM or SAXS. Specifically, we focus on the popular molecular dynamics flexible fitting (MDFF) method, which has been widely used for flexible fitting into cryo-EM maps. Second, we describe hybrid molecular dynamics, Rosetta Monte-Carlo and minimum ensemble search (MES) methods that can be used to incorporate SAXS into pseudoatomic structural models. We present concise descriptions of the two methods and their most popular alternatives, along with select illustrative applications to protein/nucleic acid assemblies involved in DNA replication and repair.
Collapse
Affiliation(s)
- Xiaojun Xu
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30302, USA
| | - Chunli Yan
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30302, USA
| | - Robert Wohlhueter
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30302, USA
| | - Ivaylo Ivanov
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30302, USA
| |
Collapse
|
19
|
Singharoy A, Venkatakrishnan B, Liu Y, Mayne CG, Lee S, Chen CH, Zlotnick A, Schulten K, Flood AH. Macromolecular Crystallography for Synthetic Abiological Molecules: Combining xMDFF and PHENIX for Structure Determination of Cyanostar Macrocycles. J Am Chem Soc 2015; 137:8810-8. [PMID: 26121416 DOI: 10.1021/jacs.5b04407] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Crystal structure determination has long provided insight into structure and bonding of small molecules. When those same small molecules are designed to come together in multimolecular assemblies, such as in coordination cages, supramolecular architectures and organic-based frameworks, their crystallographic characteristics closely resemble biological macromolecules. This resemblance suggests that biomacromolecular refinement approaches be used for structure determination of abiological molecular complexes that arise in an aggregate state. Following this suggestion we investigated the crystal structure of a pentagonal macrocycle, cyanostar, by means of biological structure analysis methods and compared results to traditional small molecule methods. Cyanostar presents difficulties seen in supramolecular crystallography including whole molecule disorder and highly flexible solvent molecules sitting in macrocyclic and intermolecule void spaces. We used the force-field assisted refinement method, molecular dynamics flexible fitting algorithm for X-ray crystallography (xMDFF), along with tools from the macromolecular structure determination suite PHENIX. We found that a standard implementation of PHENIX, namely one without xMDFF, either fails to produce a solution by molecular replacement alone or produces an inaccurate structure when using generic geometry restraints, even at a very high diffraction data resolution of 0.84 Å. The problems disappear when taking advantage of xMDFF, which applies an optimized force field to realign molecular models during phasing by providing accurate restraints. The structure determination for this model system shows excellent agreement with the small-molecule methods. Therefore, the joint xMDFF-PHENIX refinement protocol provides a new strategy that uses macromolecule methods for structure determination of small molecules and their assemblies.
Collapse
Affiliation(s)
- Abhishek Singharoy
- †Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 North Mathews Avenue, Urbana, Illinois 61801, United States
| | - Balasubramanian Venkatakrishnan
- ‡Molecular and Cellular Biochemistry Department, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405, United States
| | - Yun Liu
- §Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Christopher G Mayne
- †Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 North Mathews Avenue, Urbana, Illinois 61801, United States
| | - Semin Lee
- §Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Chun-Hsing Chen
- §Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Adam Zlotnick
- ‡Molecular and Cellular Biochemistry Department, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405, United States
| | - Klaus Schulten
- †Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 North Mathews Avenue, Urbana, Illinois 61801, United States.,∥Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, United States
| | - Amar H Flood
- §Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| |
Collapse
|
20
|
Vashisth H. Flexibility in the insulin receptor ectodomain enables docking of insulin in crystallographic conformation observed in a hormone-bound microreceptor. MEMBRANES 2014; 4:730-46. [PMID: 25309993 PMCID: PMC4289863 DOI: 10.3390/membranes4040730] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 09/18/2014] [Accepted: 10/05/2014] [Indexed: 12/11/2022]
Abstract
Insulin binding to the insulin receptor (IR) is the first key step in initiating downstream signaling cascades for glucose homeostasis in higher organisms. The molecular details of insulin recognition by IR are not yet completely understood, but a picture of hormone/receptor interactions at one of the epitopes (Site 1) is beginning to emerge from recent structural evidence. However, insulin-bound structures of truncated IR suggest that crystallographic conformation of insulin cannot be accommodated in the full IR ectodomain due to steric overlap of insulin with the first two type III fibronectin domains (F1 and F2), which are contributed to the insulin binding-pocket by the second subunit in the IR homodimer. A conformational change in the F1-F2 pair has thus been suggested. In this work, we present an all-atom structural model of complex of insulin and the IR ectodomain, where no structural overlap of insulin with the receptor domains (F1 and F2) is observed. This structural model was arrived at by flexibly fitting parts of our earlier insulin/IR all-atom model into the simulated density maps of crystallized constructs combined with conformational sampling from apo-IR solution conformations. Importantly, our experimentally-consistent model helps rationalize yet unresolved Site.
Collapse
Affiliation(s)
- Harish Vashisth
- Department of Chemical Engineering, University of New Hampshire, 33 Academic Way, Durham,NH 03824, USA.
| |
Collapse
|
21
|
Vashisth H, Skiniotis G, Brooks CL. Collective variable approaches for single molecule flexible fitting and enhanced sampling. Chem Rev 2014; 114:3353-65. [PMID: 24446720 PMCID: PMC3983124 DOI: 10.1021/cr4005988] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Indexed: 12/12/2022]
Affiliation(s)
- Harish Vashisth
- Department
of Chemical Engineering, University of New
Hampshire, Durham, New Hampshire 03824, United States
| | - Georgios Skiniotis
- Life Sciences Institute, Department
of Biological Chemistry, and
Biophysics Program, and Department of Chemistry and Biophysics Program, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Charles Lee Brooks
- Life Sciences Institute, Department
of Biological Chemistry, and
Biophysics Program, and Department of Chemistry and Biophysics Program, University of Michigan, Ann Arbor, Michigan 48109, United States
| |
Collapse
|
22
|
Spiga E, Degiacomi MT, Dal Peraro M. New Strategies for Integrative Dynamic Modeling of Macromolecular Assembly. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2014; 96:77-111. [DOI: 10.1016/bs.apcsb.2014.06.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
|
23
|
Fernández IS, Bai XC, Hussain T, Kelley AC, Lorsch JR, Ramakrishnan V, Scheres SH. Molecular architecture of a eukaryotic translational initiation complex. Science 2013; 342:1240585. [PMID: 24200810 PMCID: PMC3836175 DOI: 10.1126/science.1240585] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The last step in eukaryotic translational initiation involves the joining of the large and small subunits of the ribosome, with initiator transfer RNA (Met-tRNA(i)(Met)) positioned over the start codon of messenger RNA in the P site. This step is catalyzed by initiation factor eIF5B. We used recent advances in cryo-electron microscopy (cryo-EM) to determine a structure of the eIF5B initiation complex to 6.6 angstrom resolution from <3% of the population, comprising just 5143 particles. The structure reveals conformational changes in eIF5B, initiator tRNA, and the ribosome that provide insights into the role of eIF5B in translational initiation. The relatively high resolution obtained from such a small fraction of a heterogeneous sample suggests a general approach for characterizing the structure of other dynamic or transient biological complexes.
Collapse
Affiliation(s)
- Israel S. Fernández
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, CB2 0QH, United Kingdom
| | - Xiao-Chen Bai
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, CB2 0QH, United Kingdom
| | - Tanweer Hussain
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, CB2 0QH, United Kingdom
| | - Ann C. Kelley
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, CB2 0QH, United Kingdom
| | - Jon R. Lorsch
- Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD, USA
| | - V. Ramakrishnan
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, CB2 0QH, United Kingdom
| | - Sjors H.W. Scheres
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, CB2 0QH, United Kingdom
| |
Collapse
|
24
|
Abstract
The ultrastructure of bacteria is only accessible by electron microscopy. Our insights into the architecture of cells and cellular compartments such as the envelope and appendages is thus dependent on the progress of preparative and imaging techniques in electron microscopy. Here, I give a short overview of the development and characteristics of methods applied for imaging (components of) the bacterial surface and refer to key investigations and exemplary results. In the beginning of electron microscopy, fixation of biological material and staining for contrast enhancement were the standard techniques. The results from freeze-etching, metal shadowing and from ultrathin-sections of plastic-embedded material shaped our view of the cellular organization of bacteria. The introduction of cryo-preparations, keeping samples in their natural environment, and three-dimensional (3D) electron microscopy of isolated protein complexes and intact cells opened the door to a new dimension and has provided insight into the native structure of macromolecules and the in situ organization of cells at molecular resolution. Cryo-electron microscopy of single particles, together with other methods of structure determination, and cellular cryo-electron tomography will provide us with a quasi-atomic model of the bacterial cell surface in the years to come.
Collapse
|
25
|
Zhang K, Wang L, Liu Y, Chan KY, Pang X, Schulten K, Dong Z, Sun F. Flexible interwoven termini determine the thermal stability of thermosomes. Protein Cell 2013; 4:432-44. [PMID: 23709365 DOI: 10.1007/s13238-013-3026-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2013] [Accepted: 04/26/2013] [Indexed: 01/27/2023] Open
Abstract
Group II chaperonins, which assemble as double-ring complexes, assist in the refolding of nascent peptides or denatured proteins in an ATP-dependent manner. The molecular mechanism of group II chaperonin assembly and thermal stability is yet to be elucidated. Here, we selected the group II chaperonins (cpn-α and cpn-β), also called thermosomes, from Acidianus tengchongensis and investigated their assembly and thermal stability. We found that the binding of ATP or its analogs contributed to the successful assembly of thermosomes and enhanced their thermal stabilities. Cpn-β is more thermally stable than cpn-α, while the thermal stability of the hetero thermosome cpn-αβ is intermediate. Cryo-electron microscopy reconstructions of cpn-α and cpn-β revealed the interwoven densities of their non-conserved flexible N/C-termini around the equatorial planes. The deletion or swapping of their termini and pH-dependent thermal stability assays revealed the key role of the termini electrostatic interactions in the assembly and thermal stability of the thermosomes.
Collapse
Affiliation(s)
- Kai Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | | | | | | | | | | | | | | |
Collapse
|
26
|
Vashisth H, Skiniotis G, Brooks CL. Enhanced sampling and overfitting analyses in structural refinement of nucleic acids into electron microscopy maps. J Phys Chem B 2013; 117:3738-46. [PMID: 23506287 DOI: 10.1021/jp3126297] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Flexible fitting computational algorithms are often useful to interpret low-resolution maps of many macromolecular complexes generated by electron microscopy (EM) imaging. One such atomistic simulation technique is molecular dynamics flexible fitting (MDFF), which has been widely applied to generate structural models of large ribonucleoprotein assemblies such as the ribosome. We have previously shown that MDFF simulations of globular proteins are sensitive to the resolution of the target EM map and the strength of restraints used to preserve the secondary structure elements during fitting (Vashisth, H.; et al. Structure 2012, 20, 1453-1462). In this work, we aim to systematically examine the quality of structural models of various nucleic acids obtained via MDFF by varying the map resolution and the strength of structural restraints. We also demonstrate how an enhanced conformational sampling technique for proteins, temperature-accelerated molecular dynamics (TAMD), can be combined with MDFF for the structural refinement of nucleic acids in EM maps. Finally, we also demonstrate application of TAMD-assisted MDFF (TAMDFF) on a RNA/protein complex and suggest that TAMDFF is a viable strategy for enhanced conformational fitting in target maps of ribonucleoprotein complexes.
Collapse
Affiliation(s)
- Harish Vashisth
- Department of Chemistry and Biophysics Program, Department of Biological Chemistry, and Biophysics Program, University of Michigan , Ann Arbor, Michigan, USA
| | | | | |
Collapse
|
27
|
Vashisth H, Skiniotis G, Brooks CL. Using enhanced sampling and structural restraints to refine atomic structures into low-resolution electron microscopy maps. Structure 2013; 20:1453-62. [PMID: 22958641 DOI: 10.1016/j.str.2012.08.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 07/30/2012] [Accepted: 08/06/2012] [Indexed: 01/14/2023]
Abstract
For a variety of problems in structural biology, low-resolution maps generated by electron microscopy imaging are often interpreted with the help of various flexible-fitting computational algorithms. In this work, we systematically analyze the quality of final models of various proteins obtained via molecular dynamics flexible fitting (MDFF) by varying the map-resolution, strength of structural restraints, and the steering forces. We find that MDFF can be extended to understand conformational changes in lower-resolution maps if larger structural restraints and lower steering forces are used to prevent overfitting. We further show that the capabilities of MDFF can be extended by combining it with an enhanced conformational sampling method, temperature-accelerated molecular dynamics (TAMD). Specifically, either TAMD can be used to generate better starting configurations for MDFF fitting or TAMD-assisted MDFF (TAMDFF) can be performed to accelerate conformational search in atomistic simulations.
Collapse
Affiliation(s)
- Harish Vashisth
- Department of Chemistry and Biophysics Program, University of Michigan, 930 North University Avenue, Chem 2006, Ann Arbor, MI 48109, USA.
| | | | | |
Collapse
|
28
|
Wang X, Xu F, Liu J, Gao B, Liu Y, Zhai Y, Ma J, Zhang K, Baker TS, Schulten K, Zheng D, Pang H, Sun F. Atomic model of rabbit hemorrhagic disease virus by cryo-electron microscopy and crystallography. PLoS Pathog 2013; 9:e1003132. [PMID: 23341770 PMCID: PMC3547835 DOI: 10.1371/journal.ppat.1003132] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 11/29/2012] [Indexed: 02/03/2023] Open
Abstract
Rabbit hemorrhagic disease, first described in China in 1984, causes hemorrhagic necrosis of the liver. Its etiological agent, rabbit hemorrhagic disease virus (RHDV), belongs to the Lagovirus genus in the family Caliciviridae. The detailed molecular structure of any lagovirus capsid has yet to be determined. Here, we report a cryo-electron microscopic (cryoEM) reconstruction of wild-type RHDV at 6.5 Å resolution and the crystal structures of the shell (S) and protruding (P) domains of its major capsid protein, VP60, each at 2.0 Å resolution. From these data we built a complete atomic model of the RHDV capsid. VP60 has a conserved S domain and a specific P2 sub-domain that differs from those found in other caliciviruses. As seen in the shell portion of the RHDV cryoEM map, which was resolved to ∼5.5 Å, the N-terminal arm domain of VP60 folds back onto its cognate S domain. Sequence alignments of VP60 from six groups of RHDV isolates revealed seven regions of high variation that could be mapped onto the surface of the P2 sub-domain and suggested three putative pockets might be responsible for binding to histo-blood group antigens. A flexible loop in one of these regions was shown to interact with rabbit tissue cells and contains an important epitope for anti-RHDV antibody production. Our study provides a reliable, pseudo-atomic model of a Lagovirus and suggests a new candidate for an efficient vaccine that can be used to protect rabbits from RHDV infection. Rabbit hemorrhagic disease (RHD), first described in China in 1984, causes hemorrhagic necrosis of the liver within three days after infection and with a mortality rate that exceeds 90%. RHD has spread to large parts of the world and threatens the rabbit industry and related ecology. Its etiological agent, rabbit hemorrhagic disease virus (RHDV), belongs to the Lagovirus genus in the family Caliciviridae. Currently, the absence of a high-resolution model of any lagovirus impedes our understanding of its molecular interactions with hosts and successful design of an efficient anti-RHDV vaccine. Here, we use hybrid structural approaches to construct a pseudo-atomic model of RHDV that reveals significant differences in the P2 sub-domain of the major capsid protein compared to that seen in other caliciviruses. We identified seven regions of high sequence variation in this sub-domain that dictate the binding specificities of histo-blood group antigens. In one of these regions, we identified an antigenic peptide that interacts with rabbit tissue cells and elicits a significant immune response in rabbits and, hence, protects them from RHDV infection. Our pseudo-atomic model provides a structural framework for developing new anti-RHDV vaccines and will also help guide use of the RHDV capsid as a vehicle to display human tumor antigens as part of anti-tumor therapy.
Collapse
Affiliation(s)
- Xue Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics (IBP), Chinese Academy of Sciences (CAS), Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Fengting Xu
- Department of Biochemistry and Molecular Biology, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Jiasen Liu
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Bingquan Gao
- National Laboratory of Biomacromolecules, Institute of Biophysics (IBP), Chinese Academy of Sciences (CAS), Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yanxin Liu
- Beckman Institute and Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Yujia Zhai
- National Laboratory of Biomacromolecules, Institute of Biophysics (IBP), Chinese Academy of Sciences (CAS), Beijing, China
| | - Jun Ma
- National Laboratory of Biomacromolecules, Institute of Biophysics (IBP), Chinese Academy of Sciences (CAS), Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Kai Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics (IBP), Chinese Academy of Sciences (CAS), Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Timothy S. Baker
- Department of Chemistry and Biochemistry and Division of Biological Sciences, University of California-San Diego, La Jolla, California, United States of America
| | - Klaus Schulten
- Beckman Institute and Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Dong Zheng
- Analytical and Testing Center, Beijing Normal University, Beijing, China
- * E-mail: (DZ); (HP); (FS)
| | - Hai Pang
- School of Medicine, Tsinghua University, Beijing, China
- * E-mail: (DZ); (HP); (FS)
| | - Fei Sun
- National Laboratory of Biomacromolecules, Institute of Biophysics (IBP), Chinese Academy of Sciences (CAS), Beijing, China
- * E-mail: (DZ); (HP); (FS)
| |
Collapse
|
29
|
Paramo T, Garzón D, Holdbrook DA, Khalid S, Bond PJ. The simulation approach to lipid-protein interactions. Methods Mol Biol 2013; 974:435-455. [PMID: 23404287 DOI: 10.1007/978-1-62703-275-9_19] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The interactions between lipids and proteins are crucial for a range of biological processes, from the folding and stability of membrane proteins to signaling and metabolism facilitated by lipid-binding proteins. However, high-resolution structural details concerning functional lipid/protein interactions are scarce due to barriers in both experimental isolation of native lipid-bound complexes and subsequent biophysical characterization. The molecular dynamics (MD) simulation approach provides a means to complement available structural data, yielding dynamic, structural, and thermodynamic data for a protein embedded within a physiologically realistic, modelled lipid environment. In this chapter, we provide a guide to current methods for setting up and running simulations of membrane proteins and soluble, lipid-binding proteins, using standard atomistically detailed representations, as well as simplified, coarse-grained models. In addition, we outline recent studies that illustrate the power of the simulation approach in the context of biologically relevant lipid/protein interactions.
Collapse
Affiliation(s)
- Teresa Paramo
- Department of Chemistry, Unilever Centre for Molecular Informatics, University of Cambridge, Cambridge, UK
| | | | | | | | | |
Collapse
|
30
|
Chandler DE, Penin F, Schulten K, Chipot C. The p7 protein of hepatitis C virus forms structurally plastic, minimalist ion channels. PLoS Comput Biol 2012; 8:e1002702. [PMID: 23028296 PMCID: PMC3447957 DOI: 10.1371/journal.pcbi.1002702] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 07/27/2012] [Indexed: 12/20/2022] Open
Abstract
Hepatitis C virus (HCV) p7 is a membrane-associated oligomeric protein harboring ion channel activity. It is essential for effective assembly and release of infectious HCV particles and an attractive target for antiviral intervention. Yet, the self-assembly and molecular mechanism of p7 ion channelling are currently only partially understood. Using molecular dynamics simulations (aggregate time 1.2 µs), we show that p7 can form stable oligomers of four to seven subunits, with a bias towards six or seven subunits, and suggest that p7 self-assembles in a sequential manner, with tetrameric and pentameric complexes forming as intermediate states leading to the final hexameric or heptameric assembly. We describe a model of a hexameric p7 complex, which forms a transiently-open channel capable of conducting ions in simulation. We investigate the ability of the hexameric model to flexibly rearrange to adapt to the local lipid environment, and demonstrate how this model can be reconciled with low-resolution electron microscopy data. In the light of these results, a view of p7 oligomerization is proposed, wherein hexameric and heptameric complexes may coexist, forming minimalist, yet robust functional ion channels. In the absence of a high-resolution p7 structure, the models presented in this paper can prove valuable as a substitute structure in future studies of p7 function, or in the search for p7-inhibiting drugs.
Collapse
Affiliation(s)
- Danielle E. Chandler
- Department of Physics and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - François Penin
- Bases Moléculaires et Structurales des Systèmes Infectieux, IBCP, Université Lyon 1, Univ Lyon, France; CNRS, UMR 5086, Lyon, France
| | - Klaus Schulten
- Department of Physics and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Christophe Chipot
- Beckman Institute, University of Illinois at Urbana-Champaign Urbana, Illinois, United States of America
- Équipe de Dynamique des Assemblages Membranaires UMR 7565, Université de Lorraine, Vanduvre-lès-Nancy, France
| |
Collapse
|
31
|
|
32
|
Gumbart J, Schreiner E, Wilson DN, Beckmann R, Schulten K. Mechanisms of SecM-mediated stalling in the ribosome. Biophys J 2012; 103:331-41. [PMID: 22853911 DOI: 10.1016/j.bpj.2012.06.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Revised: 06/01/2012] [Accepted: 06/05/2012] [Indexed: 02/05/2023] Open
Abstract
Nascent-peptide modulation of translation is a common regulatory mechanism of gene expression. In this mechanism, while the nascent peptide is still in the exit tunnel of the ribosome, it induces translational pausing, thereby controlling the expression of downstream genes. One example is SecM, which inhibits peptide-bond formation in the ribosome's peptidyl transferase center (PTC) during its own translation, upregulating the expression of the protein translocase SecA. Although biochemical experiments and cryo-electron microscopy data have led to the identification of some residues involved in SecM recognition, the full pathway of interacting residues that connect SecM to the PTC through the ribosome has not yet been conclusively established. Here, using the cryo-electron microscopy data, we derived the first (to our knowledge) atomic model of the SecM-stalled ribosome via molecular-dynamics flexible fitting, complete with P- and A-site tRNAs. Subsequently, we carried out simulations of native and mutated SecM-stalled ribosomes to investigate possible interaction pathways between a critical SecM residue, R163, and the PTC. In particular, the simulations reveal the role of SecM in altering the position of the tRNAs in the ribosome, and thus demonstrate how the presence of SecM in the exit tunnel induces stalling. Finally, steered molecular-dynamics simulations in which SecM was pulled toward the tunnel exit suggest how SecA interacting with SecM from outside the ribosome relieves stalling.
Collapse
Affiliation(s)
- James Gumbart
- Biosciences Division, Argonne National Laboratory, Argonne, Illinois, USA
| | | | | | | | | |
Collapse
|
33
|
Henderson R, Sali A, Baker ML, Carragher B, Devkota B, Downing KH, Egelman EH, Feng Z, Frank J, Grigorieff N, Jiang W, Ludtke SJ, Medalia O, Penczek PA, Rosenthal PB, Rossmann MG, Schmid MF, Schröder GF, Steven AC, Stokes DL, Westbrook JD, Wriggers W, Yang H, Young J, Berman HM, Chiu W, Kleywegt GJ, Lawson CL. Outcome of the first electron microscopy validation task force meeting. Structure 2012; 20:205-14. [PMID: 22325770 PMCID: PMC3328769 DOI: 10.1016/j.str.2011.12.014] [Citation(s) in RCA: 374] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 12/29/2011] [Accepted: 12/29/2011] [Indexed: 11/10/2022]
Abstract
This Meeting Review describes the proceedings and conclusions from the inaugural meeting of the Electron Microscopy Validation Task Force organized by the Unified Data Resource for 3DEM (http://www.emdatabank.org) and held at Rutgers University in New Brunswick, NJ on September 28 and 29, 2010. At the workshop, a group of scientists involved in collecting electron microscopy data, using the data to determine three-dimensional electron microscopy (3DEM) density maps, and building molecular models into the maps explored how to assess maps, models, and other data that are deposited into the Electron Microscopy Data Bank and Protein Data Bank public data archives. The specific recommendations resulting from the workshop aim to increase the impact of 3DEM in biology and medicine.
Collapse
Affiliation(s)
- Richard Henderson
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Wereszczynski J, McCammon JA. Simulations of the p97 complex suggest novel conformational states of hydrolysis intermediates. Protein Sci 2012; 21:475-86. [PMID: 22238181 DOI: 10.1002/pro.2024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 12/16/2011] [Accepted: 01/04/2011] [Indexed: 11/07/2022]
Abstract
The vitally important AAA (ATPases associated with various cellular activities) protein p97 is involved in cellular functions ranging from replication to degradation of misfolded proteins and has recently been proposed as a novel chemotherapeutic target. p97 is a large molecular machine that has been shown to hexamerize in vitro, with each monomer consisting of an N domain responsible for binding to effector proteins and two AAA repeats (D1 and D2). However, structural studies are inconclusive or in disagreement with one another on several important features such as the locations of the N domains, the relative orientations of the D1 and D2 rings, and the dimensions of the central pore. Here, we present atomic-scale simulations of the p97 hexamer in the prehydrolysis, transition, and post-hydrolysis states. To improve the agreement between low- and high-resolution experimental studies, we first use a biased simulation technique, molecular dynamics flexible fitting (MDFF), to improve the correlation between the structures described in these experiments. We follow this with extended, classical molecular dynamics simulations, which not only show that structures generated in the MDFF phase are stable, but reveal insights into the dynamics important to each state. Simulation results suggest a hybrid model for hydrolysis, in which the N and D2 domains are dynamic while the D1 domains are relatively static, salt bridges stabilize the position of the N domains in the pre-hydrolysis state, and the rings formed by D1 and D2 rotate relative to one another.
Collapse
Affiliation(s)
- Jeff Wereszczynski
- The Department of Chemistry and Biochemistry, University of California, San Diego, USA.
| | | |
Collapse
|
35
|
Chan KY, Gumbart J, McGreevy R, Watermeyer JM, Sewell BT, Schulten K. Symmetry-restrained flexible fitting for symmetric EM maps. Structure 2011; 19:1211-8. [PMID: 21893283 DOI: 10.1016/j.str.2011.07.017] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 07/21/2011] [Accepted: 07/28/2011] [Indexed: 01/25/2023]
Abstract
Many large biological macromolecules have inherent structural symmetry, being composed of a few distinct subunits, repeated in a symmetric array. These complexes are often not amenable to traditional high-resolution structural determination methods, but can be imaged in functionally relevant states using cryo-electron microscopy (cryo-EM). A number of methods for fitting atomic-scale structures into cryo-EM maps have been developed, including the molecular dynamics flexible fitting (MDFF) method. However, quality and resolution of the cryo-EM map are the major determinants of a method's success. In order to incorporate knowledge of structural symmetry into the fitting procedure, we developed the symmetry-restrained MDFF method. The new method adds to the cryo-EM map-derived potential further restraints on the allowed conformations of a complex during fitting, thereby improving the quality of the resultant structure. The benefit of using symmetry-based restraints during fitting, particularly for medium to low-resolution data, is demonstrated for three different systems.
Collapse
Affiliation(s)
- Kwok-Yan Chan
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | | | | | | | | | | |
Collapse
|
36
|
Excited states of ribosome translocation revealed through integrative molecular modeling. Proc Natl Acad Sci U S A 2011; 108:18943-8. [PMID: 22080606 DOI: 10.1073/pnas.1108363108] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The dynamic nature of biomolecules leads to significant challenges when characterizing the structural properties associated with function. While X-ray crystallography and imaging techniques (such as cryo-electron microscopy) can reveal the structural details of stable molecular complexes, strategies must be developed to characterize configurations that exhibit only marginal stability (such as intermediates) or configurations that do not correspond to minima on the energy landscape (such as transition-state ensembles). Here, we present a methodology (MDfit) that utilizes molecular dynamics simulations to generate configurations of excited states that are consistent with available biophysical and biochemical measurements. To demonstrate the approach, we present a sequence of configurations that are suggested to be associated with transfer RNA (tRNA) movement through the ribosome (translocation). The models were constructed by combining information from X-ray crystallography, cryo-electron microscopy, and biochemical data. These models provide a structural framework for translocation that may be further investigated experimentally and theoretically to determine the precise energetic character of each configuration and the transition dynamics between them.
Collapse
|
37
|
Hsin J, LaPointe LM, Kazy A, Chipot C, Senes A, Schulten K. Oligomerization state of photosynthetic core complexes is correlated with the dimerization affinity of a transmembrane helix. J Am Chem Soc 2011; 133:14071-81. [PMID: 21790140 PMCID: PMC3168531 DOI: 10.1021/ja204869h] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In the Rhodobacter (Rba.) species of photosynthetic purple bacteria, a single transmembrane α-helix, PufX, is found within the core complex, an essential photosynthetic macromolecular assembly that performs the absorption and the initial processing of light energy. Despite its structural simplicity, many unresolved questions surround PufX, the most important of which is its location within the photosynthetic core complex. One proposed placement of PufX is at the center of a core complex dimer, where two PufX helices associate in the membrane and form a homodimer. Inability for PufX of certain Rba. species to form a homodimer is thought to lead to monomeric core complexes. In the present study, we employ a combination of computational and experimental techniques to test the hypothesized homodimerization of PufX. We carry out a systematic investigation to measure the dimerization affinity of PufX from four Rba. species, Rba. blasticus , Rba. capsulatus , Rba. sphaeroides , and Rba. veldkampii , using a molecular dynamics-based free-energy method, as well as experimental TOXCAT assays. We found that the four PufX helices have substantially different dimerization affinities. Both computational and experimental techniques demonstrate that species with dimeric core complexes have PufX that can potentially form a homodimer, whereas the one species with monomeric core complexes has a PufX with little to no dimerization propensity. Our analysis of the helix-helix interface revealed a number of positions that may be important for PufX dimerization and the formation of a hydrogen-bond network between these GxxxG-containing helices. Our results suggest that the different oligomerization states of core complexes in various Rba. species can be attributed, among other factors, to the different propensity of its PufX helix to homodimerize.
Collapse
|
38
|
Strunk BS, Loucks CR, Su M, Vashisth H, Cheng S, Schilling J, Brooks CL, Karbstein K, Skiniotis G. Ribosome assembly factors prevent premature translation initiation by 40S assembly intermediates. Science 2011; 333:1449-53. [PMID: 21835981 DOI: 10.1126/science.1208245] [Citation(s) in RCA: 185] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Ribosome assembly in eukaryotes requires approximately 200 essential assembly factors (AFs) and occurs through ordered events that initiate in the nucleolus and culminate in the cytoplasm. Here, we present the electron cryo-microscopy (cryo-EM) structure of a late cytoplasmic 40S ribosome assembly intermediate from Saccharomyces cerevisiae at 18 angstrom resolution. We obtained cryo-EM reconstructions of preribosomal complexes lacking individual components to define the positions of all seven AFs bound to this intermediate. These late-binding AFs are positioned to prevent each step in the translation initiation pathway. Together, they obstruct the binding sites for initiation factors, prevent the opening of the messenger RNA channel, block 60S subunit joining, and disrupt the decoding site. These redundant mechanisms probably ensure that pre-40S particles do not enter the translation pathway, which would result in their rapid degradation.
Collapse
Affiliation(s)
- Bethany S Strunk
- Chemical Biology Doctoral Program, University of Michigan, Ann Arbor, MI 48109, USA
| | | | | | | | | | | | | | | | | |
Collapse
|