Two mutations that alter the regulatory activity of E. coli recA protein

Abstract

The E. coli recA gene product is a direct participant and a central regulatory element in important processes of DNA repair. It has the direct function of catalyzing pairing of single-stranded DNA to a homologous region in duplex DNA, a reaction thought to be fundamental to genetic recombination. This activity of recA protein probably contributes to DNA repair by promoting recombination between damaged DNA molecules. The recA protein has a regulatory function, mediated by its ability to destroy repressors and possibly other proteins by proteolytic cleavage, leading to the induction of certain genes. recA protein is activated to cleave repressors in vitro by interaction with ATP (or an ATP analog) and a polynucleotide such as single-stranded DNA. The same interaction probably initiates the strandpairing reaction. recA protein may also be activated to attack repressors in vivo when it interacts with single-stranded DNA; DNA-damaging treatments such as UV-irradiation would thereby invoke the recA-dependent functions of recombination, repair, mutagenesis and prophage induction. As further evidence that the proteolytic activity of recA protein is responsible for its regulatory function, the ability of 2 mutationally altered recA proteins to cleave phage .lambda. repressor correlated with the ability of the mutant cells to induce prophage.