Anti-vacuolar ATPase assembly factor VMA21 antibodies are used for the immunodetection of the protein encoded by the VMA21 gene. In humans, the canonical protein has a reported length of 101 amino acid residues and a mass of 11.4 kDa. Its subcellular localization is in the cytoplasmic vesicles and ER. Alternative splicing is reported to yield 2 different isoforms for this protein. A member of the VMA21 protein family, it is known to be required for the assembly of the V0 complex of the vacuolar ATPase (V-ATPase) in the endoplasmic reticulum. The gene encoding this protein is implicated in Myopathy. Other names for this target antigen include VMA21 vacuolar H+-ATPase homolog, VMA21, vacuolar ATPase assembly factor, myopathy with excessive autophagy protein, and vacuolar ATPase assembly integral membrane protein VMA21. Gene orthologs have been identified in the mouse, rat, bovine, frog, zebrafish, chimpanzee and chicken species.