Crystal structure of yeast V-ATPase subunit C reveals its stator function

Vacuolar H⁺-ATPase (V-ATPase) has a crucial role in the vacuolar system of eukaryotic cells. It provides most of the energy required for transport systems that utilize the proton-motive force that is generated by ATP hydrolysis. Some, but not all, of the V-ATPase subunits are homologous to those of F-ATPase and the nonhomologous subunits determine the unique features of V-ATPase. We determined the crystal structure of V-ATPase subunit C (Vma5p), which does not show any homology with F-ATPase subunits, at 1.75 Å resolution. The structural features suggest that subunit C functions as a flexible stator that holds together the catalytic and membrane sectors of the enzyme. A second crystal form that was solved at 2.9 Å resolution supports the flexible nature of subunit C. These structures provide a framework for exploring the unique mechanistic features of V-ATPases.