A 100 kDa vanadate and lanzoprazole-sensitive ATPase from Streptococcus mutans membrane

The cariogenic potential of Streptococcus mutans is due to the production of organic acids derived from energy metabolism, which implies the need of mechanisms for the organism to tolerate this acidic environment. The F(1)F(o)-ATPase is generally considered as the main enzyme responsible for cytoplasmic proton extrusion, but mutations that resulted in a 50% reduction in F(1)F(o)-ATPase activity in S. mutans still allowed the micro-organism to grow and extrude acid, keeping the intracellular pH one pH unit above the extracellular ambient. This finding suggests the existence of other enzymatic (or cellular) mechanisms that keep the cytosolic pH neutral during micro-organism growth. This paper describes a membrane protein in S. mutans, with a molecular weight of 100 kDa, which exhibits ATPase activity inhibited by classic inhibitors of P-type ATPases (orthovanadate) and H(+),K(+)-ATPase (lanzoprazole), has an optimum pH comparable to other H(+)-ATPases and undergoes phosphorylation during the catalytic reaction, like that of H(+)-ATPases described in yeast and plant plasma membrane. Together, these results strongly suggest that the enzyme we describe here is a P-type H(+)-ATPase or H(+),ion-ATPase that can act in association with F(1)F(o)-ATPase during the growth of the S. mutans.