NEW MUTATIONS IN AND AROUND THE L2 DISORDERED LOOP OF THE RECA PROTEIN MODULATE RECOMBINATION AND OR COPROTEASE ACTIVITY

The RecA protein plays a key role in Escherichia coli recombination and DNA repair. We have created new recA mutants with mutations in the vicinity of the recA430 mutation (Gly-204-->Ser) which is known to affect RecA coprotease activity. Mutants carrying recA659 or recA611, located 3 and 7 amino acids downstream of residue 204, respectively, lose all RecA activities, while the mutant carrying recA616, which is located at 12 amino acids from this residue, keeps the coprotease activity but is unable to promote recombination. Complementation experiments show that both mutations recA611 and recA659 are dominant over the wild-type or recA430 allele while recA616 seems to be recessive to recA+ and dominant over recA430. It is suggested that these mutations are located in RecA domains which direct conformational modifications.