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:8349704, PubMed:27295975). V-ATPase is responsible for acidifying and maintaining the pH of intracellular compartments (PubMed:8349704, PubMed:27295975). This subunit is essential for activity, but not assembly, of the enzyme complex (PubMed:8349704, PubMed:27295975). This subunit is also required for silencing the ATPase activity of V-ATPase when V1 is detached from V0 (PubMed:27295975). 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:8349704, PubMed:25971514, PubMed:18055462, PubMed:27295975). Interacts with YND1 (PubMed:10954728). Increases the ATPase activity of membrane-detached V-ATPase V1 (PubMed:27295975). Abolishes growth at pH 7.5 and in the presence of calcium chloride, abrogates growth at pH 5.0 (PubMed:27295975). Present with 22500 molecules/cell in log phase SD medium. Belongs to the V-ATPase H subunit family.