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 (By similarity). Required for assembly and activity of the vacuolar ATPase (By similarity). Regulates the size of gut granules during embryonic development (PubMed:20148972). In neurons, required for necrotic cell death by promoting intracellular acidification (PubMed:16005300). Required for cell death induced by hypoxia (PubMed:16005300). Required for acidification of synaptic vesicles and the release of neurotransmitters from adult neurons (PubMed:22426883). 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). Ubiquitous expression in embryos. Expressed in gonads, intestine, neurons in the head and motoneurons in the ventral cord of larvae and adults (PubMed:11110798). Expressed in the vulvae and spermathecal uterine valves (PubMed:11441002). Weakly expressed in the pharynx (PubMed:11441002). Specifically expressed in the nervous system. Specifically expressed in the nervous system. Expressed in embryos, larvae and adult. Highest level of expression is in early embryos (PubMed:11110798). Expressed in the nerve ring and ventral nerve cord in L1 larvae (PubMed:11441002). RNAi-mediated knockdown causes embryonic lethality at the 100-cell stage. Belongs to the V-ATPase 116 kDa subunit family.