title: The intrinsically disordered linker of E. coli SSB is critical for the release from single-stranded DNA.
abstract: The Escherichia coli single stranded DNA binding protein (SSB) is crucial for DNA replication, recombination and repair. Within each process, it has two seemingly disparate roles: it stabilizes single-stranded DNA (ssDNA) intermediates generated during DNA processing and, forms complexes with a group of proteins known as the SSB-interactome. Key to both roles is the C-terminal, one-third of the protein, in particular the intrinsically disordered linker (IDL). Previously, they have shown using a series of linker deletion mutants that the IDL links both ssDNA and target protein binding by mediating interactions with the oligosaccharide/oligonucleotide binding fold in the target. In this study, they examine the role of the linker region in SSB function in a variety of DNA metabolic processes in vitro. Using the same linker mutants, the results show that in addition to association reactions (either DNA or protein), the IDL is critical for the release of SSB from DNA. This release can be under conditions of ssDNA competition or active displacement by a DNA helicase or recombinase. Consistent with their previous work these results indicate that SSB linker mutants are defective for SSB-SSB interactions, and when the IDL is removed a terminal SSB-DNA complex results. Formation of this complex inhibits downstream processing of DNA by helicases such as RecG or PriA as well as recombination, mediated by RecA. A model, based on the evidence herein, is presented to explain how the IDL acts in SSB function.
authors.affiliation: Department of Microbiology and Immunology, Center for Single Molecule Biophysics, University at Buffalo, Buffalo, New York.
authors.forename: Hui Yin
authors.initials: HY
authors.lastname: Tan
authors.affiliation: Department of Microbiology and Immunology, Center for Single Molecule Biophysics, University at Buffalo, Buffalo, New York.
authors.forename: Luke A
authors.initials: LA
authors.lastname: Wilczek
authors.affiliation: Department of Microbiology and Immunology, Center for Single Molecule Biophysics, University at Buffalo, Buffalo, New York.
authors.forename: Sasheen
authors.initials: S
authors.lastname: Pottinger
authors.affiliation: Departament de Física Fonamental, Facultat de Física, Universitat de Barcelona, Diagonal 647, 08028, Barcelona, Spain.|CIBER-BBN de Bioingenieria, Biomateriales y Nanomedicina, Instituto de Sanidad Carlos III, Madrid, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Manosas
authors.affiliation: Department of Microbiology and Immunology, Center for Single Molecule Biophysics, University at Buffalo, Buffalo, New York.
authors.forename: Cong
authors.initials: C
authors.lastname: Yu
authors.affiliation: Department of Microbiology and Immunology, Center for Single Molecule Biophysics, University at Buffalo, Buffalo, New York.
authors.forename: Trong
authors.initials: T
authors.lastname: Nguyenduc
authors.affiliation: Department of Microbiology and Immunology, Center for Single Molecule Biophysics, University at Buffalo, Buffalo, New York.
authors.forename: Piero R
authors.initials: PR
authors.lastname: Bianco
mesh_terms: D020816:Amino Acid Motifs; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D064267:Intrinsically Disordered Proteins; D000072417:Protein Domains
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D064267:Intrinsically Disordered Proteins; C476430:SSB protein, E coli; C071446:RecG protein, E coli; C506743:priA protein, E coli; D004265:DNA Helicases
keywords: OB-fold; PXXP motif; RecG; SH3 domain; SSB; ssDNA binding