Subunit of the V1 complex of vacuolar(H+)-ATPase (V-ATPase), a multisubunit enzyme composed of a peripheral complex (V1) that hydrolyzes ATP and a membrane integral complex (V0) that translocates protons (PubMed:10781598, PubMed:11777935, PubMed:1730668, PubMed:8416931). V-ATPase is responsible for acidifying and maintaining the pH of intracellular compartments (PubMed:8416931). Subunit C is necessary for the assembly of the catalytic sector of the enzyme and is likely to have a specific function in its catalytic activity (PubMed:15792803). Reversibly leaves the enzyme after glucose depletion, causing the catalytic subcomplex V1 to detach from the V0 section (PubMed:15792803). V-ATPase is a heteromultimeric enzyme composed of a peripheral catalytic V1 complex (components A to H) attached to an integral membrane V0 proton pore complex (components: a, c, c', c'', d, e, f and VOA1) (PubMed:25971514). Interacts directly with VMA4 (PubMed:15751969). Present with 21114 molecules/cell in log phase SD medium. Belongs to the V-ATPase C subunit family.