Open AccessRecBCD-dependent joint molecule formation promoted by the Escherichia coli RecA and SSB proteins.
Author(s) -
Linda J. Roman,
Dan A. Dixon,
Stephen C. Kowalczykowski
Publication year - 1991
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.88.8.3367
Subject(s) - recbcd , dna , homologous recombination , escherichia coli , biology , dna supercoil , dna repair , biophysics , mutant , sos response , microbiology and biotechnology , biochemistry , chemistry , dna replication , gene
We describe the formation of homologously paired joint molecules in an in vitro reaction that is dependent on the concerted actions of purified RecA and RecBCD proteins and is stimulated by single-stranded DNA-binding protein (SSB). RecBCD enzyme initiates the process by unwinding the linear double-stranded DNA to produce single-stranded DNA, which is trapped by SSB and RecA. RecA uses this single-stranded DNA to catalyze the invasion of a supercoiled double-stranded DNA molecule, forming a homologously paired joint molecule. At low RecBCD enzyme concentrations, the rate-limiting step is the unwinding of duplex DNA by RecBCD, whereas at higher RecBCD concentrations, the rate-limiting step is RecA-catalyzed strand invasion. The behavior of mutant RecA proteins in this in vitro reaction parallels their in vivo phenotypes, suggesting that this reaction may define biochemical steps that occur during homologous recombination by the RecBCD pathway in vivo.