Site-directed mutagenesis in the Escherichia coli recA gene.

Escherichia coli RecA protein plays a fundamental role in genetic recombination and in regulation and expression of the SOS response. We have constructed 6 mutants in the recA gene by site-directed mutagenesis, 5 of which were located in the vicinity of the recA430 mutation responsible for a coprotease deficient phenotype and one which was at the Tyr 264 site. We have analysed the capacity of these mutants to accomplish recombination and to express SOS functions. Our results suggest that the region including amino acid 204 and at least 7 amino acids downstream interacts not only with LexA protein but also with ATP. In addition, the mutation at Tyr 264 shows that this amino acid is essential for RecA activities in vivo, probably because of its involvement in an ATP binding site, as previously shown in vitro.