1031227060ENSG00000110719ENSMUSG00000001750Q13488n/aNM_006019NM_006053NM_001351059NM_001136091NM_001167784NM_016921NP_006010NP_006044NP_001337988n/aV-type proton ATPase 116 kDa subunit a isoform 3 is an enzyme that in humans is encoded by the TCIRG1 gene. 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 protein isoforms 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 composed of a cytosolic V1 domain and a transmembrane V0 domain.