Phosphatidylinositol-linked red blood cell membrane proteins and blood group antigens

A new class of membrane proteins has recently been described. Unlike integral membrane proteins, which traverse the membrane with one or more hydrophobic peptide domains, the peptide domains of these more newly described proteins are entirely extracellular and are anchored to the cell membrane via a phosphatidylinositol-glycan (GPI) anchor. Erythrocyte membrane proteins of this class include proteins with diverse functions; several, however, are complement regulatory proteins. Moreover, it is the lack of expression of GPI-anchored proteins that is responsible for manifestations of the acquired hematologic disease paroxysmal nocturnal hemoglobinuria. Recently, several investigators have also demonstrated that a number of erythrocyte blood group antigens reside on this class of proteins. These antigens include those of the Cromer blood group, JMH, Holley/Gregory, Cartwright, and Dombrock. The biochemical basis for the Cromer, JMH, and Holley/Gregory antigens have so far been partly delineated.