1
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Newcomb ESP, Douma LG, Morris LA, Bloom LB. The Escherichia coli clamp loader rapidly remodels SSB on DNA to load clamps. Nucleic Acids Res 2022; 50:12872-12884. [PMID: 36511874 PMCID: PMC9825162 DOI: 10.1093/nar/gkac1169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 12/06/2022] [Indexed: 12/15/2022] Open
Abstract
Single-stranded DNA binding proteins (SSBs) avidly bind ssDNA and yet enzymes that need to act during DNA replication and repair are not generally impeded by SSB, and are often stimulated by SSB. Here, the effects of Escherichia coli SSB on the activities of the DNA polymerase processivity clamp loader were investigated. SSB enhances binding of the clamp loader to DNA by increasing the lifetime on DNA. Clamp loading was measured on DNA substrates that differed in length of ssDNA overhangs to permit SSB binding in different binding modes. Even though SSB binds DNA adjacent to single-stranded/double-stranded DNA junctions where clamps are loaded, the rate of clamp loading on DNA was not affected by SSB on any of the DNA substrates. Direct measurements of the relative timing of DNA-SSB remodeling and enzyme-DNA binding showed that the clamp loader rapidly remodels SSB on DNA such that SSB has little effect on DNA binding rates. However, when SSB was mutated to reduce protein-protein interactions with the clamp loader, clamp loading was inhibited by impeding binding of the clamp loader to DNA. Thus, protein-protein interactions between the clamp loader and SSB facilitate rapid DNA-SSB remodeling to allow rapid clamp loader-DNA binding and clamp loading.
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Affiliation(s)
- Elijah S P Newcomb
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610-0245, USA
| | - Lauren G Douma
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610-0245, USA
| | - Leslie A Morris
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610-0245, USA
| | - Linda B Bloom
- To whom correspondence should be addressed. Tel: +1 352 294 8379; Fax: +1 352 392 2953;
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2
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Vallejo DD, Rojas Ramírez C, Parson KF, Han Y, Gadkari VV, Ruotolo BT. Mass Spectrometry Methods for Measuring Protein Stability. Chem Rev 2022; 122:7690-7719. [PMID: 35316030 DOI: 10.1021/acs.chemrev.1c00857] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mass spectrometry is a central technology in the life sciences, providing our most comprehensive account of the molecular inventory of the cell. In parallel with developments in mass spectrometry technologies targeting such assessments of cellular composition, mass spectrometry tools have emerged as versatile probes of biomolecular stability. In this review, we cover recent advancements in this branch of mass spectrometry that target proteins, a centrally important class of macromolecules that accounts for most biochemical functions and drug targets. Our efforts cover tools such as hydrogen-deuterium exchange, chemical cross-linking, ion mobility, collision induced unfolding, and other techniques capable of stability assessments on a proteomic scale. In addition, we focus on a range of application areas where mass spectrometry-driven protein stability measurements have made notable impacts, including studies of membrane proteins, heat shock proteins, amyloidogenic proteins, and biotherapeutics. We conclude by briefly discussing the future of this vibrant and fast-moving area of research.
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Affiliation(s)
- Daniel D Vallejo
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Carolina Rojas Ramírez
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Kristine F Parson
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Yilin Han
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Varun V Gadkari
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Brandon T Ruotolo
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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3
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Seraphim TV, Nano N, Cheung YWS, Aluksanasuwan S, Colleti C, Mao YQ, Bhandari V, Young G, Höll L, Phanse S, Gordiyenko Y, Southworth DR, Robinson CV, Thongboonkerd V, Gava LM, Borges JC, Babu M, Barbosa LRS, Ramos CHI, Kukura P, Houry WA. Assembly principles of the human R2TP chaperone complex reveal the presence of R2T and R2P complexes. Structure 2022; 30:156-171.e12. [PMID: 34492227 DOI: 10.1016/j.str.2021.08.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 07/16/2021] [Accepted: 08/10/2021] [Indexed: 11/18/2022]
Abstract
R2TP is a highly conserved chaperone complex formed by two AAA+ ATPases, RUVBL1 and RUVBL2, that associate with PIH1D1 and RPAP3 proteins. R2TP acts in promoting macromolecular complex formation. Here, we establish the principles of R2TP assembly. Three distinct RUVBL1/2-based complexes are identified: R2TP, RUVBL1/2-RPAP3 (R2T), and RUVBL1/2-PIH1D1 (R2P). Interestingly, we find that PIH1D1 does not bind to RUVBL1/RUVBL2 in R2TP and does not function as a nucleotide exchange factor; instead, RPAP3 is found to be the central subunit coordinating R2TP architecture and linking PIH1D1 and RUVBL1/2. We also report that RPAP3 contains an intrinsically disordered N-terminal domain mediating interactions with substrates whose sequences are primarily enriched for Armadillo repeat domains and other helical-type domains. Our work provides a clear and consistent model of R2TP complex structure and gives important insights into how a chaperone machine concerned with assembly of folded proteins into multisubunit complexes might work.
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Affiliation(s)
- Thiago V Seraphim
- Department of Biochemistry, University of Toronto, 661 University Avenue, MaRS Centre, West Tower, Room 1612, Toronto, ON M5G 1M1, Canada; Department of Chemistry and Biochemistry, University of Regina, Regina, SK S4S 0A2, Canada
| | - Nardin Nano
- Department of Biochemistry, University of Toronto, 661 University Avenue, MaRS Centre, West Tower, Room 1612, Toronto, ON M5G 1M1, Canada
| | - Yiu Wing Sunny Cheung
- Department of Biochemistry, University of Toronto, 661 University Avenue, MaRS Centre, West Tower, Room 1612, Toronto, ON M5G 1M1, Canada
| | - Siripat Aluksanasuwan
- Department of Biochemistry, University of Toronto, 661 University Avenue, MaRS Centre, West Tower, Room 1612, Toronto, ON M5G 1M1, Canada; Medical Proteomics Unit, Office for Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Carolina Colleti
- Department of Biochemistry, University of Toronto, 661 University Avenue, MaRS Centre, West Tower, Room 1612, Toronto, ON M5G 1M1, Canada; Center of Biological and Health Sciences, Federal University of São Carlos, São Carlos, SP 13560-970, Brazil
| | - Yu-Qian Mao
- Department of Biochemistry, University of Toronto, 661 University Avenue, MaRS Centre, West Tower, Room 1612, Toronto, ON M5G 1M1, Canada
| | - Vaibhav Bhandari
- Department of Biochemistry, University of Toronto, 661 University Avenue, MaRS Centre, West Tower, Room 1612, Toronto, ON M5G 1M1, Canada
| | - Gavin Young
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
| | - Larissa Höll
- Department of Chemistry and Biochemistry, University of Regina, Regina, SK S4S 0A2, Canada
| | - Sadhna Phanse
- Department of Biochemistry, University of Toronto, 661 University Avenue, MaRS Centre, West Tower, Room 1612, Toronto, ON M5G 1M1, Canada; Department of Chemistry and Biochemistry, University of Regina, Regina, SK S4S 0A2, Canada
| | - Yuliya Gordiyenko
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
| | - Daniel R Southworth
- Department of Biochemistry and Biophysics, Institute for Neurodegenerative Diseases, University of California, San Francisco, CA 94158, USA
| | - Carol V Robinson
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
| | - Visith Thongboonkerd
- Medical Proteomics Unit, Office for Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Lisandra M Gava
- Center of Biological and Health Sciences, Federal University of São Carlos, São Carlos, SP 13560-970, Brazil
| | - Júlio C Borges
- São Carlos Institute of Chemistry, University of São Paulo, São Carlos, SP 13566-590, Brazil
| | - Mohan Babu
- Department of Chemistry and Biochemistry, University of Regina, Regina, SK S4S 0A2, Canada
| | - Leandro R S Barbosa
- Institute of Physics, University of São Paulo, São Paulo, SP 05508-090, Brazil; Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, SP 13083-100, Brazil
| | - Carlos H I Ramos
- Institute of Chemistry, University of Campinas (UNICAMP), Campinas, SP 13083-970, Brazil
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
| | - Walid A Houry
- Department of Biochemistry, University of Toronto, 661 University Avenue, MaRS Centre, West Tower, Room 1612, Toronto, ON M5G 1M1, Canada; Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada.
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4
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Monachino E, Jergic S, Lewis JS, Xu ZQ, Lo ATY, O'Shea VL, Berger JM, Dixon NE, van Oijen AM. A Primase-Induced Conformational Switch Controls the Stability of the Bacterial Replisome. Mol Cell 2020; 79:140-154.e7. [PMID: 32464091 DOI: 10.1016/j.molcel.2020.04.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 03/12/2020] [Accepted: 04/20/2020] [Indexed: 12/16/2022]
Abstract
Recent studies of bacterial DNA replication have led to a picture of the replisome as an entity that freely exchanges DNA polymerases and displays intermittent coupling between the helicase and polymerase(s). Challenging the textbook model of the polymerase holoenzyme acting as a stable complex coordinating the replisome, these observations suggest a role of the helicase as the central organizing hub. We show here that the molecular origin of this newly found plasticity lies in the 500-fold increase in strength of the interaction between the polymerase holoenzyme and the replicative helicase upon association of the primase with the replisome. By combining in vitro ensemble-averaged and single-molecule assays, we demonstrate that this conformational switch operates during replication and promotes recruitment of multiple holoenzymes at the fork. Our observations provide a molecular mechanism for polymerase exchange and offer a revised model for the replication reaction that emphasizes its stochasticity.
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Affiliation(s)
- Enrico Monachino
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, and Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia; Zernike Institute for Advanced Materials, University of Groningen, Groningen 9747, the Netherlands
| | - Slobodan Jergic
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, and Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Jacob S Lewis
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, and Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Zhi-Qiang Xu
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, and Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Allen T Y Lo
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, and Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Valerie L O'Shea
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - James M Berger
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Nicholas E Dixon
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, and Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia.
| | - Antoine M van Oijen
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, and Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia.
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5
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Perera HM, Behrmann MS, Hoang JM, Griffin WC, Trakselis MA. Contacts and context that regulate DNA helicase unwinding and replisome progression. Enzymes 2019; 45:183-223. [PMID: 31627877 DOI: 10.1016/bs.enz.2019.08.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Hexameric DNA helicases involved in the separation of duplex DNA at the replication fork have a universal architecture but have evolved from two separate protein families. The consequences are that the regulation, translocation polarity, strand specificity, and architectural orientation varies between phage/bacteria to that of archaea/eukaryotes. Once assembled and activated for single strand DNA translocation and unwinding, the DNA polymerase couples tightly to the helicase forming a robust replisome complex. However, this helicase-polymerase interaction can be challenged by various forms of endogenous or exogenous agents that can stall the entire replisome or decouple DNA unwinding from synthesis. The consequences of decoupling can be severe, leading to a build-up of ssDNA requiring various pathways for replication fork restart. All told, the hexameric helicase sits prominently at the front of the replisome constantly responding to a variety of obstacles that require transient unwinding/reannealing, traversal of more stable blocks, and alternations in DNA unwinding speed that regulate replisome progression.
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Affiliation(s)
- Himasha M Perera
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Megan S Behrmann
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Joy M Hoang
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Wezley C Griffin
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Michael A Trakselis
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States.
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6
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Abstract
DNA replication in Escherichia coli initiates at oriC, the origin of replication and proceeds bidirectionally, resulting in two replication forks that travel in opposite directions from the origin. Here, we focus on events at the replication fork. The replication machinery (or replisome), first assembled on both forks at oriC, contains the DnaB helicase for strand separation, and the DNA polymerase III holoenzyme (Pol III HE) for DNA synthesis. DnaB interacts transiently with the DnaG primase for RNA priming on both strands. The Pol III HE is made up of three subassemblies: (i) the αɛθ core polymerase complex that is present in two (or three) copies to simultaneously copy both DNA strands, (ii) the β2 sliding clamp that interacts with the core polymerase to ensure its processivity, and (iii) the seven-subunit clamp loader complex that loads β2 onto primer-template junctions and interacts with the α polymerase subunit of the core and the DnaB helicase to organize the two (or three) core polymerases. Here, we review the structures of the enzymatic components of replisomes, and the protein-protein and protein-DNA interactions that ensure they remain intact while undergoing substantial dynamic changes as they function to copy both the leading and lagging strands simultaneously during coordinated replication.
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Affiliation(s)
- J S Lewis
- Centre for Medical & Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - S Jergic
- Centre for Medical & Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia
| | - N E Dixon
- Centre for Medical & Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia.
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7
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Montón Silva A, Lapenta F, Stefan A, Dal Piaz F, Ceccarelli A, Perrone A, Hochkoeppler A. Simultaneous ternary extension of DNA catalyzed by a trimeric replicase assembled in vivo. Biochem Biophys Res Commun 2015; 462:14-20. [PMID: 25918025 DOI: 10.1016/j.bbrc.2015.04.067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 04/12/2015] [Indexed: 10/23/2022]
Abstract
According to current models, dimeric DNA Polymerases coordinate the replication of DNA leading and lagging strands. However, it was recently shown that trimeric DNA Polymerases, assembled in vitro, replicate the lagging strand more efficiently than dimeric replicases. Here we show that the τ, α, ε, and θ subunits of Escherichia coli DNA Polymerase III can be assembled in vivo, yielding the trimeric τ3α3ε3θ3 complex. Further, we propose a molecular model of this complex, whose catalytic action was investigated using model DNA substrates. Our observations indicate that trimeric DNA replicases reduce the gap between leading and lagging strand synthesis.
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Affiliation(s)
- Alejandro Montón Silva
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Fabio Lapenta
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Alessandra Stefan
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy; CSGI, University of Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, FI, Italy
| | - Fabrizio Dal Piaz
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, SA, Italy
| | - Alessandro Ceccarelli
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Alessandro Perrone
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Alejandro Hochkoeppler
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy; CSGI, University of Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, FI, Italy.
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8
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Saliou JM, Manival X, Tillault AS, Atmanene C, Bobo C, Branlant C, Van Dorsselaer A, Charpentier B, Cianférani S. Combining native MS approaches to decipher archaeal box H/ACA ribonucleoprotein particle structure and activity. Proteomics 2015; 15:2851-61. [DOI: 10.1002/pmic.201400529] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Revised: 02/06/2015] [Accepted: 02/24/2015] [Indexed: 12/23/2022]
Affiliation(s)
- Jean-Michel Saliou
- BioOrganic Mass Spectrometry Laboratory (LSMBO); IPHC; Université de Strasbourg; Strasbourg France
- IPHC; CNRS UMR 7178; Strasbourg France
| | - Xavier Manival
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA); UMR 7365 CNRS Université de Lorraine; Biopôle Vandœuvre-lès-Nancy France
| | - Anne-Sophie Tillault
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA); UMR 7365 CNRS Université de Lorraine; Biopôle Vandœuvre-lès-Nancy France
| | - Cédric Atmanene
- BioOrganic Mass Spectrometry Laboratory (LSMBO); IPHC; Université de Strasbourg; Strasbourg France
- IPHC; CNRS UMR 7178; Strasbourg France
| | - Claude Bobo
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA); UMR 7365 CNRS Université de Lorraine; Biopôle Vandœuvre-lès-Nancy France
| | - Christiane Branlant
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA); UMR 7365 CNRS Université de Lorraine; Biopôle Vandœuvre-lès-Nancy France
| | - Alain Van Dorsselaer
- BioOrganic Mass Spectrometry Laboratory (LSMBO); IPHC; Université de Strasbourg; Strasbourg France
- IPHC; CNRS UMR 7178; Strasbourg France
| | - Bruno Charpentier
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA); UMR 7365 CNRS Université de Lorraine; Biopôle Vandœuvre-lès-Nancy France
| | - Sarah Cianférani
- BioOrganic Mass Spectrometry Laboratory (LSMBO); IPHC; Université de Strasbourg; Strasbourg France
- IPHC; CNRS UMR 7178; Strasbourg France
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9
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Topological models of heteromeric protein assemblies from mass spectrometry: application to the yeast eIF3:eIF5 complex. ACTA ACUST UNITED AC 2014; 22:117-28. [PMID: 25544043 PMCID: PMC4306531 DOI: 10.1016/j.chembiol.2014.11.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 10/07/2014] [Accepted: 11/07/2014] [Indexed: 02/05/2023]
Abstract
Describing, understanding, and modulating the function of the cell require elucidation of the structures of macromolecular assemblies. Here, we describe an integrative method for modeling heteromeric complexes using as a starting point disassembly pathways determined by native mass spectrometry (MS). In this method, the pathway data and other available information are encoded as a scoring function on the positions of the subunits of the complex. The method was assessed on its ability to reproduce the native contacts in five benchmark cases with simulated MS data and two cases with real MS data. To illustrate the power of our method, we purified the yeast initiation factor 3 (eIF3) complex and characterized it by native MS and chemical crosslinking MS. We established substoichiometric binding of eIF5 and derived a model for the five-subunit eIF3 complex, at domain level, consistent with its role as a scaffold for other initiation factors. Integrative MS method allows topological characterization of heteromeric complexes Intersubunit crosslinks increase the precision of the predicted topologies A 3D model of eIF3:eIF5 complex was built using restraints from MS-based methods Integrative modeling reveals two submodules within eIF3: eIF3b:i:g and eIF3a:c
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10
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Integrative modelling coupled with ion mobility mass spectrometry reveals structural features of the clamp loader in complex with single-stranded DNA binding protein. J Mol Biol 2013; 425:4790-801. [PMID: 23583780 DOI: 10.1016/j.jmb.2013.04.006] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 03/14/2013] [Accepted: 04/03/2013] [Indexed: 01/26/2023]
Abstract
DNA polymerase III, a decameric 420-kDa assembly, simultaneously replicates both strands of the chromosome in Escherichia coli. A subassembly of this holoenzyme, the seven-subunit clamp loader complex, is responsible for loading the sliding clamp (β2) onto DNA. Here, we use structural information derived from ion mobility mass spectrometry (IM-MS) to build three-dimensional models of one form of the full clamp loader complex, γ3δδ'ψχ (254 kDa). By probing the interaction between the clamp loader and a single-stranded DNA (ssDNA) binding protein (SSB4) and by identifying two distinct conformational states, with and without ssDNA, we assemble models of ψχ-SSB4 (108 kDa) and the clamp loader-SSB4 (340 kDa) consistent with IM data. A significant increase in measured collision cross-section (~10%) of the clamp loader-SSB4 complex upon DNA binding suggests large conformational rearrangements. This DNA bound conformation represents the active state and, along with the presence of ψχ, stabilises the clamp loader-SSB4 complex. Overall, this study of a large heteromeric complex analysed by IM-MS, coupled with integrative modelling, highlights the potential of such an approach to reveal structural features of previously unknown complexes of high biological importance.
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11
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Afonso JP, Chintakayala K, Suwannachart C, Sedelnikova S, Giles K, Hoyes JB, Soultanas P, Rafferty JB, Oldham NJ. Insights into the structure and assembly of the Bacillus subtilis clamp-loader complex and its interaction with the replicative helicase. Nucleic Acids Res 2013; 41:5115-26. [PMID: 23525462 PMCID: PMC3643586 DOI: 10.1093/nar/gkt173] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The clamp-loader complex plays a crucial role in DNA replication by loading the β-clamp onto primed DNA to be used by the replicative polymerase. Relatively little is known about the stoichiometry, structure and assembly pathway of this complex, and how it interacts with the replicative helicase, in Gram-positive organisms. Analysis of full and partial complexes by mass spectrometry revealed that a hetero-pentameric τ3-δ-δ' Bacillus subtilis clamp-loader assembles via multiple pathways, which differ from those exhibited by the Gram-negative model Escherichia coli. Based on this information, a homology model of the B. subtilis τ3-δ-δ' complex was constructed, which revealed the spatial positioning of the full C-terminal τ domain. The structure of the δ subunit was determined by X-ray crystallography and shown to differ from that of E. coli in the nature of the amino acids comprising the τ and δ' binding regions. Most notably, the τ-δ interaction appears to be hydrophilic in nature compared with the hydrophobic interaction in E. coli. Finally, the interaction between τ3 and the replicative helicase DnaB was driven by ATP/Mg(2+) conformational changes in DnaB, and evidence is provided that hydrolysis of one ATP molecule by the DnaB hexamer is sufficient to stabilize its interaction with τ3.
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Affiliation(s)
- José P Afonso
- School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
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12
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Hyung SJ, Ruotolo BT. Integrating mass spectrometry of intact protein complexes into structural proteomics. Proteomics 2012; 12:1547-64. [PMID: 22611037 DOI: 10.1002/pmic.201100520] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
MS analysis of intact protein complexes has emerged as an established technology for assessing the composition and connectivity within dynamic, heterogeneous multiprotein complexes at low concentrations and in the context of mixtures. As this technology continues to move forward, one of the main challenges is to integrate the information content of such intact protein complex measurements with other MS approaches in structural biology. Methods such as H/D exchange, oxidative foot-printing, chemical cross-linking, affinity purification, and ion mobility separation add complementary information that allows access to every level of protein structure and organization. Here, we survey the structural information that can be retrieved by such experiments, demonstrate the applicability of integrative MS approaches in structural proteomics, and look to the future to explore upcoming innovations in this rapidly advancing area.
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Affiliation(s)
- Suk-Joon Hyung
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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13
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Stengel F, Aebersold R, Robinson CV. Joining forces: integrating proteomics and cross-linking with the mass spectrometry of intact complexes. Mol Cell Proteomics 2011; 11:R111.014027. [PMID: 22180098 PMCID: PMC3316738 DOI: 10.1074/mcp.r111.014027] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein assemblies are critical for cellular function and understanding their physical organization is the key aim of structural biology. However, applying conventional structural biology approaches is challenging for transient, dynamic, or polydisperse assemblies. There is therefore a growing demand for hybrid technologies that are able to complement classical structural biology methods and thereby broaden our arsenal for the study of these important complexes. Exciting new developments in the field of mass spectrometry and proteomics have added a new dimension to the study of protein-protein interactions and protein complex architecture. In this review, we focus on how complementary mass spectrometry-based techniques can greatly facilitate structural understanding of protein assemblies.
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Affiliation(s)
- Florian Stengel
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Oxford, OX1 3TA United Kingdom
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14
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Abstract
Bacterial replicases are complex, tripartite replicative machines. They contain a polymerase, polymerase III (Pol III), a β₂ processivity factor, and a DnaX complex ATPase that loads β₂ onto DNA and chaperones Pol III onto the newly loaded β₂. Bacterial replicases are highly processive, yet cycle rapidly during Okazaki fragment synthesis in a regulated way. Many bacteria encode both a full-length τ and a shorter γ form of DnaX by a variety of mechanisms. γ appears to be uniquely placed in a single position relative to two τ protomers in a pentameric ring. The polymerase catalytic subunit of Pol III, α, contains a PHP domain that not only binds to a prototypical ε Mg²⁺-dependent exonuclease, but also contains a second Zn²⁺-dependent proofreading exonuclease, at least in some bacteria. This review focuses on a critical evaluation of recent literature and concepts pertaining to the above issues and suggests specific areas that require further investigation.
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Affiliation(s)
- Charles S McHenry
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA.
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15
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Benesch JLP, Ruotolo BT. Mass spectrometry: come of age for structural and dynamical biology. Curr Opin Struct Biol 2011; 21:641-9. [PMID: 21880480 DOI: 10.1016/j.sbi.2011.08.002] [Citation(s) in RCA: 223] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 07/21/2011] [Accepted: 08/02/2011] [Indexed: 12/19/2022]
Abstract
Over the past two decades, mass spectrometry (MS) has emerged as a bone fide approach for structural biology. MS can inform on all levels of protein organization, and enables quantitative assessments of their intrinsic dynamics. The key advantages of MS are that it is a sensitive, high-resolution separation technique with wide applicability, and thereby allows the interrogation of transient protein assemblies in the context of complex mixtures. Here we describe how molecular-level information is derived from MS experiments, and how it can be combined with spatial and dynamical restraints obtained from other structural biology approaches to allow hybrid studies of protein architecture and movements.
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Affiliation(s)
- Justin L P Benesch
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, UK.
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16
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Park AY, Robinson CV. Protein-nucleic acid complexes and the role of mass spectrometry in their structure determination. Crit Rev Biochem Mol Biol 2011; 46:152-64. [DOI: 10.3109/10409238.2011.559451] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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17
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Integrating ion mobility mass spectrometry with molecular modelling to determine the architecture of multiprotein complexes. PLoS One 2010; 5:e12080. [PMID: 20711472 PMCID: PMC2919415 DOI: 10.1371/journal.pone.0012080] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Accepted: 07/09/2010] [Indexed: 11/21/2022] Open
Abstract
Current challenges in the field of structural genomics point to the need for new tools and technologies for obtaining structures of macromolecular protein complexes. Here, we present an integrative computational method that uses molecular modelling, ion mobility-mass spectrometry (IM-MS) and incomplete atomic structures, usually from X-ray crystallography, to generate models of the subunit architecture of protein complexes. We begin by analyzing protein complexes using IM-MS, and by taking measurements of both intact complexes and sub-complexes that are generated in solution. We then examine available high resolution structural data and use a suite of computational methods to account for missing residues at the subunit and/or domain level. High-order complexes and sub-complexes are then constructed that conform to distance and connectivity constraints imposed by IM-MS data. We illustrate our method by applying it to multimeric protein complexes within the Escherichia coli replisome: the sliding clamp, (β2), the γ complex (γ3δδ′), the DnaB helicase (DnaB6) and the Single-Stranded Binding Protein (SSB4).
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