INDUCIBILITY OF THE SOS RESPONSE IN A RECA730 STRAIN OR RECA441 STRAIN IS RESTORED BY TRANSFORMATION WITH A NEW RECA ALLELE

Escherichia coli RecA protein plays an essential role in both genetic recombination and SOS repair; in vitro RecA needs to bind ATP to promo te both activities. Residue 264 is involved in this interaction; we ha ve therefore created two new recA alleles, recA664 (Tyr264-->Glu) and recA665 (Tyr264-->His) bearing mutations at this site. As expected bot h mutations affected all RecA activities in vivo. Complementation expe riments between these new alleles and wild-type recA or recA441 or rec A730 alleles, both of which lead to constitutively activated RecA prot ein, were performed to further investigate the modulatory effects of t hese mutants on the regulation of SOS repair/recombination pathways. O ur results provide further insight into the process of polymerization of RecA protein and its regulatory functions.