title: SSB protein limits RecOR binding onto single-stranded DNA.
abstract: The RecO and RecR proteins form a complex that promotes the nucleation of RecA protein filaments onto SSB protein-coated single-stranded DNA (ssDNA). However, even when RecO and RecR proteins are provided at optimal concentrations, the loading of RecA protein is surprisingly slow, typically proceeding with a lag of 10 min or more. The rate-limiting step in RecOR-promoted RecA nucleation is the binding of RecOR protein to ssDNA, which is inhibited by SSB protein despite the documented interaction between RecO and SSB. Full activity of RecOR is seen only when RecOR is preincubated with ssDNA prior to the addition of SSB. The slow binding of RecOR to SSB-coated ssDNA involves the C terminus of SSB. When an SSB variant that lacks the C-terminal 8 amino acids is used, the capacity of RecOR to facilitate RecA loading onto the ssDNA is largely abolished. The results are used in an expanded model for RecOR action.
authors.affiliation: Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706-1544, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Hobbs
authors.forename: Akiko
authors.initials: A
authors.lastname: Sakai
authors.forename: Michael M
authors.initials: MM
authors.lastname: Cox
mesh_terms: D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D011938:Rec A Recombinases / Q000235:genetics / Q000378:metabolism
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C081006:RecO protein, E coli; C489318:RecR protein, E coli; C476430:SSB protein, E coli; D011938:Rec A Recombinases