[Recombination properties of the modified Pseudomonas aeruginosa RecA protein].

Gene recA from Pseudomonas aeruginosa was cloned into pUC19 vector under lacZ promoter. The expressed protein appeared to be modified, the aminoterminal part of deduced amino acid sequence of the RecAPa protein was found elongated by a polypeptide of 10 amino acids. The modified protein named RecAPa completely replaces RecAEc from E. coli in vivo recombination. In vitro RecAPa promotes the homologous strand transfer from a short linear duplex DNA fragment (346 bp) into circular single-stranded DNA (8196 n) being 5 times more active than RecAEc. However, when the length of dsDNA increased the difference between two proteins becomes negligible. To understand the reasons, some properties of RecAPa and RecAEc were compared. The former was shown to be more active both in binding to ssDNA in ssDNA-dependent ATP hydrolysis. The RecPa protein showed also a high affinity to dsDNA, even at a physiological pH which is known to be unfavorable for RecAEc/dsDNA binding. However, both proteins equally catalyzed the dsDNA-dependent ATP hydrolysis; we suggest that this is crucial for a full-length DNA strand transfer recombination reaction.