Background：

This gene encodes a component of vacuolar ATPase (V-ATPase)， a multisubunit enzyme that mediates acidification of eukaryotic intracellular organelles. V-ATPase dependent organelle acidification is necessary for such intracellular processes as protein sorting， zymogen activation， receptor-mediated endocytosis， and synaptic vesicle proton gradient generation. V-ATPase is composed of a cytosolic V1 domain and a transmembrane V0 domain. The V1 domain consists of three A and three B subunits， two G subunits plus the C， D， E， F， and H subunits. The V1 domain contains the ATP catalytic site. The V0 domain consists of five different subunits: a， c， c’， c’’， and d. Additional isoforms of many of the V1 and V0 subunit proteins are encoded by multiple genes or alternatively spliced transcript variants. This encoded protein is known as the D subunit and is found ubiquitously.