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 (By similarity). V-ATPase is responsible for acidifying and maintaining the pH of intracellular compartments (By similarity). This subunit is essential for activity, but not assembly, of the enzyme complex (By similarity). This subunit is also required for silencing the ATPase activity of V-ATPase when V1 is detached from V0 (By similarity). 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). Belongs to the V-ATPase H subunit family.