V-type proton ATPase 116 kDa subunit a isoform 3 is an enzyme that in humans is encoded by the TCIRG1 gene. Through alternate splicing, this gene encodes two proteins with similarity to subunits of the vacuolar ATPase (V-ATPase) but the encoded proteins seem to have different functions. V-ATPase is 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, and receptor-mediated endocytosis. V-ATPase is comprised of a cytosolic V1 domain and a transmembrane V0 domain. Mutations in this gene are associated with infantile malignant osteopetrosis. [provided by RefSeq].
Part of the proton channel of V-ATPases (By similarity). Seems to be directly involved in T-cell activation.