ATPase, H+ Transporting, Lysosomal Accessory Protein 1 (ATP6AP1)

ATP6AP1 encodes a component of a multisubunit enzyme (1 mDa MW) that mediates acidification of eukaryotic intracellular organelles. Vacuolar ATPase (V-ATPase) is composed of a cytosolic V1 (site of the ATP catalytic site) and a transmembrane V0 domain. V-ATPase dependent organelle acidification is necessary for such intracellular processes as protein sorting, zymogen activation, and receptor-mediated endocytosis. The encoded protein of this gene is approximately 45 kD and may assist in the V-ATPase-mediated acidification of neuroendocrine secretory granules.

The predicted 468-amino acid bovine protein, which they called Ac45, contains an N-terminal signal sequence and a C-terminal transmembrane domain.