Subunit of the V0 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 and in some cell types, is targeted to the plasma membrane, where it is responsible for acidifying the extracellular environment (PubMed:19741196). In the intestine, required for the rhythmic defecation behavior by promoting acidification in the gut lumen following defecation (PubMed:19741196). Also, luminal acidification is required for nutrient uptake (PubMed:19741196). V-ATPase is a heteromultimeric enzyme made up of two complexes: the ATP-hydrolytic V1 complex and the proton translocation V0 complex (By similarity). The V1 complex consists of three catalytic AB heterodimers that form a heterohexamer, three peripheral stalks each consisting of EG heterodimers, one central rotor including subunits D and F, and the regulatory subunits C and H (By similarity). The proton translocation complex V0 consists of the proton transport subunit a, a ring of proteolipid subunits c9c'', rotary subunit d, subunits e and f, and the accessory subunits vah-19/Ac45 and vah-20/PRR (By similarity). Interacts with V-type proton ATPase subunit C vha-11 (PubMed:11441002). Localizes to the apical surface of intestinal cells (PubMed:11441002). Localizes to dot-like structures, possibly P granules, in P2 cells of 4-cell stage embryos (PubMed:11441002). Expressed in P2 cell of 4-cell stage embryo (at protein level) (PubMed:11441002). At the comma stage, expressed in cells in the lateral sides (at protein level) (PubMed:11441002). Specifically expressed in intestine from the 2-fold embryonic stage onwards including in the larval and adult stages (at protein level) (PubMed:11441002, PubMed:19741196). RNAi-mediated knockdown causes larval lethality at the L1 stage (PubMed:11441002). RNAi-mediated knockdown at the L1 larval stage causes reduced growth rate (PubMed:19741196). The progeny of the few that reach adulthood is arrested at the L1 larval stage (PubMed:19741196). Rhythmic defecation behavior is altered; the defecation cycle period is extended and animals have a slight arrhythmia (PubMed:19741196). In the intestinal epithelium, pH oscillates once per cycle as in the wild-type, but the oscillations are diminished in amplitude and cells are relatively acidic (PubMed:19741196). Also, luminal pH oscillations are reduced (PubMed:19741196). RNAi-mediated knockdown at the L2 larval stage causes a reduction of whole body fat mass in young adults (PubMed:19741196). In some animals, the lumen appears swollen, with a reduction of the cytoplasmic contents of intestinal cells (PubMed:19741196). Defect in nutrient absorption (PubMed:19741196). Belongs to the V-ATPase 116 kDa subunit family.