Crystal structure of a central stalk subunit C and reversible association/dissociation of vacuole-type ATPase

The vacuole-type ATPases (V-ATPases) exist in various intracellular compartments of eukaryotic cells to regulate physiological processes by controlling the acidic environment. The crystal structure of the subunit C of Thermus thermophilus V-ATPase, homologous to eukaryotic subunit d of V-ATPases, has been determined at 1.95-Angstrom resolution and located into the holoenzyme complex structure obtained by single particle analysis as suggested by the results of subunit cross-linking experiments. The result shows that V-ATPase is substantially longer than the related F-type ATPase, due to the insertion of subunit C between the V-1 (soluble) and the V-o (membrane bound) domains. Subunit C, attached to the V-o. domain, seems to have a socket like function in attaching the central-stalk subunits of the V-1 domain. This architecture seems essential for the reversible association/dissociation of the V-1 and the V-o domains, unique for V-ATPase activity regulation.