The cyanobacterium, Synechococcus sp. PCC7942, possesses two distinct genes encoding cation-transporting P-type ATPases.

P-type (or E1 E2-type) ATPases comprise a large family of prokaryotic and eukaryotic proteins capable of transporting a variety of cations, and function in a wide variety of cellular processes. The present study was carried out to search for genes encoding P-type ATPases in the phototrophic cyanobacterium, Synechococcus sp. PCC7942. We succeeded in cloning two genes each encoding P-type ATPases from this bacterium. It was found that Synechococcus at least, two distinct P-type ATPases; one belongs to the family of typical prokaryotic P-type ATPases and the other markedly resembles eukaryotic P-type ATPases. An insertion mutant lacking either of these two ATPase-genes was constructed. The results showed that the growth of these mutants is hypersensitive to osmotic stress upon addition of NaCl or sorbitol to the medium.