1
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Bonde NJ, Kozlov AG, Cox MM, Lohman TM, Keck JL. Molecular insights into the prototypical single-stranded DNA-binding protein from E. coli. Crit Rev Biochem Mol Biol 2024; 59:99-127. [PMID: 38770626 PMCID: PMC11209772 DOI: 10.1080/10409238.2024.2330372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 03/11/2024] [Indexed: 05/22/2024]
Abstract
The SSB protein of Escherichia coli functions to bind single-stranded DNA wherever it occurs during DNA metabolism. Depending upon conditions, SSB occurs in several different binding modes. In the course of its function, SSB diffuses on ssDNA and transfers rapidly between different segments of ssDNA. SSB interacts with many other proteins involved in DNA metabolism, with 22 such SSB-interacting proteins, or SIPs, defined to date. These interactions chiefly involve the disordered and conserved C-terminal residues of SSB. When not bound to ssDNA, SSB can aggregate to form a phase-separated biomolecular condensate. Current understanding of the properties of SSB and the functional significance of its many intermolecular interactions are summarized in this review.
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Affiliation(s)
- Nina J. Bonde
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Alexander G. Kozlov
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
| | - Michael M. Cox
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Timothy M. Lohman
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
| | - James L. Keck
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
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2
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Norris V, Kayser C, Muskhelishvili G, Konto-Ghiorghi Y. The roles of nucleoid-associated proteins and topoisomerases in chromosome structure, strand segregation, and the generation of phenotypic heterogeneity in bacteria. FEMS Microbiol Rev 2023; 47:fuac049. [PMID: 36549664 DOI: 10.1093/femsre/fuac049] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 12/06/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022] Open
Abstract
How to adapt to a changing environment is a fundamental, recurrent problem confronting cells. One solution is for cells to organize their constituents into a limited number of spatially extended, functionally relevant, macromolecular assemblies or hyperstructures, and then to segregate these hyperstructures asymmetrically into daughter cells. This asymmetric segregation becomes a particularly powerful way of generating a coherent phenotypic diversity when the segregation of certain hyperstructures is with only one of the parental DNA strands and when this pattern of segregation continues over successive generations. Candidate hyperstructures for such asymmetric segregation in prokaryotes include those containing the nucleoid-associated proteins (NAPs) and the topoisomerases. Another solution to the problem of creating a coherent phenotypic diversity is by creating a growth-environment-dependent gradient of supercoiling generated along the replication origin-to-terminus axis of the bacterial chromosome. This gradient is modulated by transcription, NAPs, and topoisomerases. Here, we focus primarily on two topoisomerases, TopoIV and DNA gyrase in Escherichia coli, on three of its NAPs (H-NS, HU, and IHF), and on the single-stranded binding protein, SSB. We propose that the combination of supercoiling-gradient-dependent and strand-segregation-dependent topoisomerase activities result in significant differences in the supercoiling of daughter chromosomes, and hence in the phenotypes of daughter cells.
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Affiliation(s)
- Vic Norris
- University of Rouen, Laboratory of Bacterial Communication and Anti-infection Strategies, EA 4312, 76821 Mont Saint Aignan, France
| | - Clara Kayser
- University of Rouen, Laboratory of Bacterial Communication and Anti-infection Strategies, EA 4312, 76821 Mont Saint Aignan, France
| | - Georgi Muskhelishvili
- Agricultural University of Georgia, School of Natural Sciences, 0159 Tbilisi, Georgia
| | - Yoan Konto-Ghiorghi
- University of Rouen, Laboratory of Bacterial Communication and Anti-infection Strategies, EA 4312, 76821 Mont Saint Aignan, France
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3
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Morse M, Navarro Roby F, Kinare M, McIsaac J, Williams MC, Beuning PJ. DNA damage alters binding conformations of E. coli single-stranded DNA-binding protein. Biophys J 2023; 122:3950-3958. [PMID: 37632138 PMCID: PMC10560665 DOI: 10.1016/j.bpj.2023.08.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 08/02/2023] [Accepted: 08/23/2023] [Indexed: 08/27/2023] Open
Abstract
Single-stranded DNA-binding proteins (SSBs) are essential cellular components, binding to transiently exposed regions of single-stranded DNA (ssDNA) with high affinity and sequence non-specificity to coordinate DNA repair and replication. Escherichia coli SSB (EcSSB) is a homotetramer that wraps variable lengths of ssDNA in multiple conformations (typically occupying either 65 or 35 nt), which is well studied across experimental conditions of substrate length, salt, pH, temperature, etc. In this work, we use atomic force microscopy to investigate the binding of SSB to individual ssDNA molecules. We introduce non-canonical DNA bases that mimic naturally occurring DNA damage, synthetic abasic sites, as well as a non-DNA linker into our experimental constructs at sites predicted to interact with EcSSB. By measuring the fraction of DNA molecules with EcSSB bound as well as the volume of protein bound per DNA molecule, we determine the protein binding affinity, cooperativity, and conformation. We find that, with only one damaged nucleotide, the binding of EcSSB is unchanged relative to its binding to undamaged DNA. In the presence of either two tandem abasic sites or a non-DNA spacer, however, the binding affinity associated with a single EcSSB tetramer occupying the full substrate in the 65-nt mode is greatly reduced. In contrast, the binding of two EcSSB tetramers, each in the 35-nt mode, is preserved. Changes in the binding and cooperative behaviors of EcSSB across these constructs can inform how genomic repair and replication processes may change as environmental damage accumulates in DNA.
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Affiliation(s)
- Michael Morse
- Department of Physics, Northeastern University, Boston, Massachusetts
| | - Francesco Navarro Roby
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts
| | - Mansi Kinare
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts
| | - James McIsaac
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts
| | - Mark C Williams
- Department of Physics, Northeastern University, Boston, Massachusetts.
| | - Penny J Beuning
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts.
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4
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Lee SJ, Ahn SY, Oh HB, Kim SY, Song WS, Yoon SI. Structural and Biochemical Analysis of the Recombination Mediator Protein RecR from Campylobacter jejuni. Int J Mol Sci 2023; 24:12947. [PMID: 37629127 PMCID: PMC10454854 DOI: 10.3390/ijms241612947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/15/2023] [Accepted: 08/17/2023] [Indexed: 08/27/2023] Open
Abstract
The recombination mediator complex RecFOR, consisting of the RecF, RecO, and RecR proteins, is needed to initiate homologous recombination in bacteria by positioning the recombinase protein RecA on damaged DNA. Bacteria from the phylum Campylobacterota, such as the pathogen Campylobacter jejuni, lack the recF gene and trigger homologous recombination using only RecR and RecO. To elucidate the functional properties of C. jejuni RecR (cjRecR) in recombination initiation that differ from or are similar to those in RecF-expressing bacteria, we determined the crystal structure of cjRecR and performed structure-based binding analyses. cjRecR forms a rectangular ring-like tetrameric structure and coordinates a zinc ion using four cysteine residues, as observed for RecR proteins from RecF-expressing bacteria. However, the loop of RecR that has been shown to recognize RecO and RecF in RecF-expressing bacteria is substantially shorter in cjRecR as a canonical feature of Campylobacterota RecR proteins, indicating that cjRecR lost a part of the loop in evolution due to the lack of RecF and has a low RecO-binding affinity. Furthermore, cjRecR features a larger positive patch and exhibits substantially higher ssDNA-binding affinity than RecR from RecF-expressing bacteria. Our study provides a framework for a deeper understanding of the RecOR-mediated recombination pathway.
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Affiliation(s)
- Su-jin Lee
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Si Yeon Ahn
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Han Byeol Oh
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Seung Yeon Kim
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Wan Seok Song
- Institute of Bioscience and Biotechnology, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Sung-il Yoon
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon 24341, Republic of Korea
- Institute of Bioscience and Biotechnology, Kangwon National University, Chuncheon 24341, Republic of Korea
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5
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Henry C, Mbele N, Cox MM. RecF protein targeting to postreplication (daughter strand) gaps I: DNA binding by RecF and RecFR. Nucleic Acids Res 2023; 51:5699-5713. [PMID: 37125642 PMCID: PMC10287957 DOI: 10.1093/nar/gkad311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 04/09/2023] [Accepted: 04/27/2023] [Indexed: 05/02/2023] Open
Abstract
In bacteria, the repair of post-replication gaps by homologous recombination requires the action of the recombination mediator proteins RecF, RecO and RecR. Whereas the role of the RecOR proteins to displace the single strand binding protein (SSB) and facilitate RecA loading is clear, how RecF mediates targeting of the system to appropriate sites remains enigmatic. The most prominent hypothesis relies on specific RecF binding to gap ends. To test this idea, we present a detailed examination of RecF and RecFR binding to more than 40 DNA substrates of varying length and structure. Neither RecF nor the RecFR complex exhibited specific DNA binding that can explain the targeting of RecF(R) to post-replication gaps. RecF(R) bound to dsDNA and ssDNA of sufficient length with similar facility. DNA binding was highly ATP-dependent. Most measured Kd values fell into a range of 60-180 nM. The addition of ssDNA extensions on duplex substrates to mimic gap ends or CPD lesions produces only subtle increases or decreases in RecF(R) affinity. Significant RecFR binding cooperativity was evident with many DNA substrates. The results indicate that RecF or RecFR targeting to post-replication gaps must rely on factors not yet identified, perhaps involving interactions with additional proteins.
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Affiliation(s)
- Camille Henry
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706-1544, USA
| | - Neema Mbele
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706-1544, USA
| | - Michael M Cox
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706-1544, USA
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6
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Nirwal S, Czarnocki-Cieciura M, Chaudhary A, Zajko W, Skowronek K, Chamera S, Figiel M, Nowotny M. Mechanism of RecF-RecO-RecR cooperation in bacterial homologous recombination. Nat Struct Mol Biol 2023; 30:650-660. [PMID: 37081315 DOI: 10.1038/s41594-023-00967-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 03/15/2023] [Indexed: 04/22/2023]
Abstract
In bacteria, one type of homologous-recombination-based DNA-repair pathway involves RecFOR proteins that bind at the junction between single-stranded (ss) and double-stranded (ds) DNA. They facilitate the replacement of SSB protein, which initially covers ssDNA, with RecA, which mediates the search for homologous sequences. However, the molecular mechanism of RecFOR cooperation remains largely unknown. We used Thermus thermophilus proteins to study this system. Here, we present a cryo-electron microscopy structure of the RecF-dsDNA complex, and another reconstruction that shows how RecF interacts with two different regions of the tetrameric RecR ring. Lower-resolution reconstructions of the RecR-RecO subcomplex and the RecFOR-DNA assembly explain how RecO is positioned to interact with ssDNA and SSB, which is proposed to lock the complex on a ssDNA-dsDNA junction. Our results integrate the biochemical data available for the RecFOR system and provide a framework for its complete understanding.
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Affiliation(s)
- Shivlee Nirwal
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | | | - Anuradha Chaudhary
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Weronika Zajko
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Krzysztof Skowronek
- Biophysics and Bioanalytics Facility, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Sebastian Chamera
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Małgorzata Figiel
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Marcin Nowotny
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland.
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7
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Tököli A, Bodnár B, Bogár F, Paragi G, Hetényi A, Bartus É, Wéber E, Hegedüs Z, Szabó Z, Kecskeméti G, Szakonyi G, Martinek TA. Structural Adaptation of the Single-Stranded DNA-Binding Protein C-Terminal to DNA Metabolizing Partners Guides Inhibitor Design. Pharmaceutics 2023; 15:pharmaceutics15041032. [PMID: 37111518 PMCID: PMC10143822 DOI: 10.3390/pharmaceutics15041032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 03/10/2023] [Accepted: 03/21/2023] [Indexed: 04/29/2023] Open
Abstract
Single-stranded DNA-binding protein (SSB) is a bacterial interaction hub and an appealing target for antimicrobial therapy. Understanding the structural adaptation of the disordered SSB C-terminus (SSB-Ct) to DNA metabolizing enzymes (e.g., ExoI and RecO) is essential for designing high-affinity SSB mimetic inhibitors. Molecular dynamics simulations revealed the transient interactions of SSB-Ct with two hot spots on ExoI and RecO. The residual flexibility of the peptide-protein complexes allows adaptive molecular recognition. Scanning with non-canonical amino acids revealed that modifications at both termini of SSB-Ct could increase the affinity, supporting the two-hot-spot binding model. Combining unnatural amino acid substitutions on both segments of the peptide resulted in enthalpy-enhanced affinity, accompanied by enthalpy-entropy compensation, as determined by isothermal calorimetry. NMR data and molecular modeling confirmed the reduced flexibility of the improved affinity complexes. Our results highlight that the SSB-Ct mimetics bind to the DNA metabolizing targets through the hot spots, interacting with both of segments of the ligands.
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Affiliation(s)
- Attila Tököli
- Department of Medical Chemistry, University of Szeged, H6720 Szeged, Hungary
| | - Brigitta Bodnár
- Department of Medical Chemistry, University of Szeged, H6720 Szeged, Hungary
- ELKH-SZTE Biomimetic Systems Research Group, Eötvös Loránd Research Network (ELKH), H6720 Szeged, Hungary
| | - Ferenc Bogár
- ELKH-SZTE Biomimetic Systems Research Group, Eötvös Loránd Research Network (ELKH), H6720 Szeged, Hungary
| | - Gábor Paragi
- Department of Medical Chemistry, University of Szeged, H6720 Szeged, Hungary
- Institute of Physics, University of Pécs, H7624 Pécs, Hungary
- Department of Theoretical Physics, University of Szeged, H6720 Szeged, Hungary
| | - Anasztázia Hetényi
- Department of Medical Chemistry, University of Szeged, H6720 Szeged, Hungary
| | - Éva Bartus
- Department of Medical Chemistry, University of Szeged, H6720 Szeged, Hungary
- ELKH-SZTE Biomimetic Systems Research Group, Eötvös Loránd Research Network (ELKH), H6720 Szeged, Hungary
| | - Edit Wéber
- Department of Medical Chemistry, University of Szeged, H6720 Szeged, Hungary
- ELKH-SZTE Biomimetic Systems Research Group, Eötvös Loránd Research Network (ELKH), H6720 Szeged, Hungary
| | - Zsófia Hegedüs
- Department of Medical Chemistry, University of Szeged, H6720 Szeged, Hungary
| | - Zoltán Szabó
- Department of Medical Chemistry, University of Szeged, H6720 Szeged, Hungary
| | - Gábor Kecskeméti
- Department of Medical Chemistry, University of Szeged, H6720 Szeged, Hungary
| | - Gerda Szakonyi
- Institute of Pharmaceutical Analysis, University of Szeged, H6720 Szeged, Hungary
| | - Tamás A Martinek
- Department of Medical Chemistry, University of Szeged, H6720 Szeged, Hungary
- ELKH-SZTE Biomimetic Systems Research Group, Eötvös Loránd Research Network (ELKH), H6720 Szeged, Hungary
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8
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Shinn MK, Chaturvedi SK, Kozlov AG, Lohman T. Allosteric effects of E. coli SSB and RecR proteins on RecO protein binding to DNA. Nucleic Acids Res 2023; 51:2284-2297. [PMID: 36808259 PMCID: PMC10018359 DOI: 10.1093/nar/gkad084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 01/23/2023] [Accepted: 01/25/2023] [Indexed: 02/22/2023] Open
Abstract
Escherichia coli single stranded (ss) DNA binding protein (SSB) plays essential roles in DNA maintenance. It binds ssDNA with high affinity through its N-terminal DNA binding core and recruits at least 17 different SSB interacting proteins (SIPs) that are involved in DNA replication, recombination, and repair via its nine amino acid acidic tip (SSB-Ct). E. coli RecO, a SIP, is an essential recombination mediator protein in the RecF pathway of DNA repair that binds ssDNA and forms a complex with E. coli RecR protein. Here, we report ssDNA binding studies of RecO and the effects of a 15 amino acid peptide containing the SSB-Ct monitored by light scattering, confocal microscope imaging, and analytical ultracentrifugation (AUC). We find that one RecO monomer can bind the oligodeoxythymidylate, (dT)15, while two RecO monomers can bind (dT)35 in the presence of the SSB-Ct peptide. When RecO is in molar excess over ssDNA, large RecO-ssDNA aggregates occur that form with higher propensity on ssDNA of increasing length. Binding of RecO to the SSB-Ct peptide inhibits RecO-ssDNA aggregation. RecOR complexes can bind ssDNA via RecO, but aggregation is suppressed even in the absence of the SSB-Ct peptide, demonstrating an allosteric effect of RecR on RecO binding to ssDNA. Under conditions where RecO binds ssDNA but does not form aggregates, SSB-Ct binding enhances the affinity of RecO for ssDNA. For RecOR complexes bound to ssDNA, we also observe a shift in RecOR complex equilibrium towards a RecR4O complex upon binding SSB-Ct. These results suggest a mechanism by which SSB recruits RecOR to facilitate loading of RecA onto ssDNA gaps.
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Affiliation(s)
- Min Kyung Shinn
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
- Center for Biomolecular Condensates (CBC), Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Sumit K Chaturvedi
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Biophysics, University of Delhi South Campus, New Delhi 110021, India
| | - Alexander G Kozlov
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Timothy M Lohman
- To whom correspondence should be addressed. Tel: +1 314 362 4393; Fax: +1 314 362 7183;
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9
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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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10
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Crystal Structure of the Recombination Mediator Protein RecO from Campylobacter jejuni and Its Interaction with DNA and a Zinc Ion. Int J Mol Sci 2022; 23:ijms23179667. [PMID: 36077065 PMCID: PMC9456098 DOI: 10.3390/ijms23179667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 08/19/2022] [Accepted: 08/22/2022] [Indexed: 11/23/2022] Open
Abstract
Homologous recombination is involved in repairing DNA damage, contributing to maintaining the integrity and stability of viral and cellular genomes. In bacteria, the recombination mediator proteins RecO and RecR are required to load the RecA recombinase on ssDNA for homologous recombination. To structurally and functionally characterize RecO, we determined the crystal structure of RecO from Campylobacter jejuni (cjRecO) at a 1.8 Å resolution and biochemically assessed its capacity to interact with DNA and a metal ion. cjRecO folds into a curved rod-like structure that consists of an N-terminal domain (NTD), C-terminal domain (CTD), and Zn2+-binding domain (ZnD). The ZnD at the end of the rod-like structure coordinates three cysteine residues and one histidine residue to accommodate a Zn2+ ion. Based on an extensive comparative analysis of RecO structures and sequences, we propose that the Zn2+-binding consensus sequence of RecO is CxxC…C/HxxC/H/D. The interaction with Zn2+ is indispensable for the protein stability of cjRecO but does not seem to be required for the recombination mediator function. cjRecO also interacts with ssDNA as part of its biological function, potentially using the positively charged patch in the NTD and CTD. However, cjRecO displays a low ssDNA-binding affinity, suggesting that cjRecO requires RecR to efficiently recognize ssDNA for homologous recombination.
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11
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Shen Z, Tang CM, Liu GY. Towards a better understanding of antimicrobial resistance dissemination: what can be learnt from studying model conjugative plasmids? Mil Med Res 2022; 9:3. [PMID: 35012680 PMCID: PMC8744291 DOI: 10.1186/s40779-021-00362-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 12/26/2021] [Indexed: 12/12/2022] Open
Abstract
Bacteria can evolve rapidly by acquiring new traits such as virulence, metabolic properties, and most importantly, antimicrobial resistance, through horizontal gene transfer (HGT). Multidrug resistance in bacteria, especially in Gram-negative organisms, has become a global public health threat often through the spread of mobile genetic elements. Conjugation represents a major form of HGT and involves the transfer of DNA from a donor bacterium to a recipient by direct contact. Conjugative plasmids, a major vehicle for the dissemination of antimicrobial resistance, are selfish elements capable of mediating their own transmission through conjugation. To spread to and survive in a new bacterial host, conjugative plasmids have evolved mechanisms to circumvent both host defense systems and compete with co-resident plasmids. Such mechanisms have mostly been studied in model plasmids such as the F plasmid, rather than in conjugative plasmids that confer antimicrobial resistance (AMR) in important human pathogens. A better understanding of these mechanisms is crucial for predicting the flow of antimicrobial resistance-conferring conjugative plasmids among bacterial populations and guiding the rational design of strategies to halt the spread of antimicrobial resistance. Here, we review mechanisms employed by conjugative plasmids that promote their transmission and establishment in Gram-negative bacteria, by following the life cycle of conjugative plasmids.
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Affiliation(s)
- Zhen Shen
- Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK.,Department of Laboratory Medicine, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China
| | - Christoph M Tang
- Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK
| | - Guang-Yu Liu
- Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK.
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12
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Ingram ZM, Scull NW, Schneider DS, Lucius AL. Multi-start Evolutionary Nonlinear OpTimizeR (MENOTR): A hybrid parameter optimization toolbox. Biophys Chem 2021; 279:106682. [PMID: 34634538 DOI: 10.1016/j.bpc.2021.106682] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Revised: 09/10/2021] [Accepted: 09/10/2021] [Indexed: 10/20/2022]
Abstract
Parameter optimization or "data fitting" is a computational process that identifies a set of parameter values that best describe an experimental data set. Parameter optimization is commonly carried out using a computer program utilizing a non-linear least squares (NLLS) algorithm. These algorithms work by continuously refining a user supplied initial guess resulting in a systematic increase in the goodness of fit. A well-understood problem with this class of algorithms is that in the case of models with correlated parameters the optimized output parameters are initial guess dependent. This dependency can potentially introduce user bias into the resultant analysis. While many optimization programs exist, few address this dilemma. Here we present a data analysis tool, MENOTR, that is capable of overcoming the initial guess dependence in parameter optimization. Several case studies with published experimental data are presented to demonstrate the capabilities of this tool. The results presented here demonstrate how to effectively overcome the initial guess dependence of NLLS leading to greater confidence that the resultant optimized parameters are the best possible set of parameters to describe an experimental data set. While the optimization strategies implemented within MENOTR are not entirely novel, the application of these strategies to optimize parameters in kinetic and thermodynamic biochemical models is uncommon. MENOTR was designed to require minimal modification to accommodate a new model making it immediately accessible to researchers with a limited programming background. We anticipate that this toolbox can be used in a wide variety of data analysis applications. Prototype versions of this toolbox have been used in a number of published investigations already, as well as ongoing work with chemical-quenched flow, stopped-flow, and molecular tweezers data sets. STATEMENT OF SIGNIFICANCE: Non-linear least squares (NLLS) is a common form of parameter optimization in biochemistry kinetic and thermodynamic investigations These algorithms are used to fit experimental data sets and report corresponding parameter values. The algorithms are fast and able to provide good quality solutions for models involving few parameters. However, initial guess dependence is a well-known drawback of this optimization strategy that can introduce user bias. An alternative method of parameter optimization are genetic algorithms (GA). Genetic algorithms do not have an initial guess dependence but are slow at arriving at the best set of fit parameters. Here, we present MENOTR, a parameter optimization toolbox utilizing a hybrid GA/NLLS algorithm. The toolbox maximizes the strength of each strategy while minimizing the inherent drawbacks.
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Affiliation(s)
- Zachariah M Ingram
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Nathaniel W Scull
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - David S Schneider
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, USA.
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Elucidating Recombination Mediator Function Using Biophysical Tools. BIOLOGY 2021; 10:biology10040288. [PMID: 33916151 PMCID: PMC8066028 DOI: 10.3390/biology10040288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 03/29/2021] [Accepted: 03/30/2021] [Indexed: 11/16/2022]
Abstract
Simple Summary This review recapitulates the initial knowledge acquired with genetics and biochemical experiments on Recombination mediator proteins in different domains of life. We further address how recent in vivo and in vitro biophysical tools were critical to deepen the understanding of RMPs molecular mechanisms in DNA and replication repair, and unveiled unexpected features. For instance, in bacteria, genetic and biochemical studies suggest a close proximity and coordination of action of the RecF, RecR and RecO proteins in order to ensure their RMP function, which is to overcome the single-strand binding protein (SSB) and facilitate the loading of the recombinase RecA onto ssDNA. In contrary to this expectation, using single-molecule fluorescent imaging in living cells, we showed recently that RecO and RecF do not colocalize and moreover harbor different spatiotemporal behavior relative to the replication machinery, suggesting distinct functions. Finally, we address how new biophysics tools could be used to answer outstanding questions about RMP function. Abstract The recombination mediator proteins (RMPs) are ubiquitous and play a crucial role in genome stability. RMPs facilitate the loading of recombinases like RecA onto single-stranded (ss) DNA coated by single-strand binding proteins like SSB. Despite sharing a common function, RMPs are the products of a convergent evolution and differ in (1) structure, (2) interaction partners and (3) molecular mechanisms. The RMP function is usually realized by a single protein in bacteriophages and eukaryotes, respectively UvsY or Orf, and RAD52 or BRCA2, while in bacteria three proteins RecF, RecO and RecR act cooperatively to displace SSB and load RecA onto a ssDNA region. Proteins working alongside to the RMPs in homologous recombination and DNA repair notably belongs to the RAD52 epistasis group in eukaryote and the RecF epistasis group in bacteria. Although RMPs have been studied for several decades, molecular mechanisms at the single-cell level are still not fully understood. Here, we summarize the current knowledge acquired on RMPs and review the crucial role of biophysical tools to investigate molecular mechanisms at the single-cell level in the physiological context.
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