An SOS Inhibitor that Binds to Free RecA Protein: The PsiB Protein

• Published in: Molecular cell Vol. 36; no. 1; pp. 121 - 130
• Main Authors: Petrova, Vessela, Chitteni-Pattu, Sindhu, Drees, Julia C., Inman, Ross B., Cox, Michael M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 09.10.2009
• Subjects: Adenosine Triphosphate - metabolism; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Conjugation, Genetic - physiology; Crossing Over, Genetic - genetics; DNA; DNA - genetics; DNA - metabolism; DNA, Circular - genetics; DNA, Circular - metabolism; DNA, Circular - ultrastructure; DNA, Single-Stranded - metabolism; DNA, Single-Stranded - ultrastructure; DNA-Binding Proteins - metabolism; Escherichia coli - physiology; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Fluorescence Polarization; Models, Genetic; Poly T - metabolism; Protein Binding - physiology; Rec A Recombinases - chemistry; Rec A Recombinases - metabolism; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Serine Endopeptidases - metabolism; SOS Response (Genetics) - physiology; DNA
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2009.07.026

The process of bacterial conjugation involves the transfer of a conjugative plasmid as a single strand. The potentially deleterious SOS response, which is normally triggered by the appearance of single-stranded DNA, is suppressed in the recipient cell by a conjugative plasmid system centered on the product of the psiB gene. The F plasmid PsiB protein inhibits all activities of the RecA protein, including DNA binding, DNA strand exchange, and LexA protein cleavage. The proteins known to negatively regulate recombinases, such as RecA or Rad51, generally work at the level of dismantling the nucleoprotein filament. However, PsiB binds to RecA protein that is free in solution. The RecA-PsiB complex impedes formation of RecA nucleoprotein filaments on DNA.