Presence of Na(+)-stimulated V-type ATPase in the membrane of a facultatively anaerobic and halophilic alkaliphile.

It was found that a facultatively anaerobic and halophilic alkaliphile, M-12 (Amphibacillus sp.), possesses a Na(+)-stimulated ATPase in the membrane. The ATPase activity was inhibited by NO3- and SCN- which are the inhibitors of V-type ATPase, but not by azide and vanadate, inhibitors of F-type ATPase and P-type ATPase, respectively. Upon the incubation of the membrane in buffer containing ATP and MgCl2, several polypeptides were released from the membrane. Among them, two major polypeptides with apparent molecular masses of 79 and 55 kDa crossreacted with an antiserum against the catalytic units (subunits A and B) of V-type ATPase from Enterococcus hirae. The N-terminal amino acid sequences of the 79 and 55 kDa polypeptides showed high similarity to those of subunits A and B of V-type ATPase from Enterococcus hirae, respectively. M-12 is likely to possess a V-type Na(+)-ATPase.