VACUOLAR-TYPE ATPASE IN A HYPERTHERMOPHILIC ARCHAEUM, THERMOCOCCUS SPKI

Membrane ATPase was purified from a hyperthermophilic heterotrophic ar chaeum, Thermococcus sp. KI, which grew anaerobically at 90 degrees C in the presence of sulfur. The purified enzyme had an optimal temperat ure of 90 degrees C and its molecular mass was estimated to be 600 kDa . It consisted of 4 subunits with molecular masses of 70, 60, 29 and 1 5 kDa. While the ATPase activity was resistant to most ATPase inhibito rs, the activity was reduced by nitrate, an inhibitor of the vacuolar (V)-type ATPase. N-terminal amino acid sequence of the 70 kDa subunit was similar to those of catalytic subunit of V-type ATPaes. This indic ates that hyperthermophilic heterotrophs have a V-type ATPase in their membranes. (C) 1996 Academic Press, Inc.