MG2+-DEPENDENT ADENOSINE-TRIPHOSPHATASE FROM STREPTOCOCCUS-FAECALIS MEMBRANES .1. ISOLATION AND SUBUNIT COMPOSITION

N,N-Dicyclohexylcarbodiimide-sensitive ATPase was isolated from S. faecalis and was shown by immunochemical methods to be homogeneous. The isolated enzyme comprises subunits of 7 types: .alpha., 55,000; .beta., 51,000; .gamma., 35,000; .delta., 20,000; h1, 16,000; .epsilon., 13,000; h2, 9500. The purified ATPase was used in the preparation of liposomes with reconstituted membranes. Measurements of the membrane potential arising in response to ATP addition and 32P-ATP exchange indicated that the isolated enzyme contains the complete set of subunits necessary for the ATPase activity in the membrane as a proton pump and ATP synthase.