CHARACTERIZATION OF A MEMBRANE-ASSOCIATED ATPASE FROM METHANOCOCCUS-VOLTAE, A METHANOGENIC MEMBER OF THE ARCHAEA

A membrane-associated ATPase with an M(r) of approximately 510,000 and containing subunits with M(r)S of 80,000 (alpha), 55,000 (beta), and 25,000 (gamma) was isolated from the methanogen Methanococcus voltae. Enzymatic activity was not affected by vanadate or azide, inhibitors of P- and F1-ATPase, respectively, but was inhibited by nitrate and bafilomycin A1, inhibitors of V1-type ATPases. Since dicyclohexylcarbodiimide inhibited the enzyme when it was present in membranes but not after the ATPase was solubilized, we suggest the presence of membrane-associated component analogous to the F0 and V0 components of both F-type and V-type ATPases. N-terminal amino acid sequence analysis of the alpha subunit showed a higher similarity to ATPases of the V-type family than to those of the F-type family.