MOLECULAR CHARACTERIZATION OF GLUCONOBACTER-OXYDANS RECA GENE AND ITSINHIBITORY EFFECT ON THE FUNCTION OF THE HOST WILD-TYPE RECA GENE

A DNA fragment containing the recA gene of Gluconobacter oxydans was i solated and further characterized for its nucleotide sequence and abil ity to functionally complement various recA mutations. When expressed in an Escherichia coli recA host, the G. oxydans recA protein could ef ficiently function in homologous recombination and DNA damage repair. The recA gene's nucleotide sequence analysis revealed a protein of 344 amino acids with a molecular mass of 38 kDa. We observed an E. coli-l ike LexA repressor-binding site in the G. oxydans recA gene promoter r egion, suggesting that a LexA-like mediated response system may exist in G. oxydans. The expression of G. oxydans recA in E. coli RR1, a rec A(+) strain, surprisingly caused a remarkable reduction of the host wi ld-type recA gene function, whereas the expression of both Serratia ma rcescens recA and Pseudomonas aeruginosa recA gene caused only a sligh t inhibitory effect on function of the host wild-type recA gene produc t. Compared with the E. coli RecA protein, the identity of the amino a cid sequence of G. oxydans RecA protein is much lower than those RecA proteins of both S. marcescens and Pseudomonas aeruginosa. This result suggests that the expression of another wild-type RecA could interfer e with host wild-type recA gene's function, and the extent of such an interference is possibly correlated to the identity of the amino acid sequence between the two classes of RecA protein.