Dicyclohexylcarbodiimide-binding protein is a subunit of the Methanosarcina barkeri ATPase complex

Membrane ATPase of Methanosarcina barkeri was inhibited by N, N'-dicyclohexylcarbodiimide (DCCD), whereas the extrinsic alpha beta complex of the same enzyme was not. Consistent with this finding, a 6,000 dalton (6 kDa) membrane protein was preferentially labeled with radioactive DCCD. The DCCD-sensitive ATPase was solubilized from the membranes with octylglucoside and purified in the presence of this detergent. The purified ATPase contained the alpha and beta subunits and also at least four additional proteins (40, 27, 23 and 6 kDa). The 6 kDa protein in the purified enzyme reacted with DCCD, indicating that it is a subunit of an integral part of the M. barkeri ATPase complex.