Anti-P antibodies enable researchers to detect and measure the P antigen in biological samples. This target is a reported synonym of the OCA2 gene, which encodes OCA2 melanosomal transmembrane protein. This protein is known to function in cell proliferation and melanocyte differentiation, among other biological roles. The human version of P has a canonical amino acid length of 838 residues and a protein mass of 92.9 kilodaltons, although 3 isoforms have been identified. It is reported to be localized in the membrane of cells. P is a member of the CitM (TC 2.A.11) transporter protein family.