The MAM blood group system consists of one antigen, MAM, carried on epithelial membrane protein 3 (EMP3). It consists of 163 amino acids, with predicted four transmembrane domains and two N-linked glycosylation sites. The protein is encoded by EMP3. There is a known association between EMP3 and CD44 (Indian blood group system), whereby MAM-negative individuals have reduced levels of CD44 and therefore express Indian blood group system antigens only very weakly.