ERMAP (erythrocyte membrane-associated protein; also Scianna blood group antigen) is a 60-66 kDa member of the BTN/MOG family, Ig-Superfamily of proteins. It is expressed on erythrocytes and erythrocyte precursors and likely serves as a cell adhesion molecule. Mature human ERMAP is a 446 amino acid (aa) type I transmembrane glycoprotein. It possesses a 126 aa extracellular domain (ECD) (aa 30-155) that contains one V-type Ig-like domain (aa 30-140). Single aa changes at Gly35, Glu47, Gly57, Pro60 and Arg81 generate distinct antigens of the Scianna blood group. There is one alternate start site at Met91 and a splice variant that shows an 11 aa substitution for aa 103-475. Over aa 30-155, human ERMAP is 56% aa identical to mouse ERMAP. In contrast to human ERMAP ECD, mouse REMAP ECD contains one extra Ig-like domain.