Immunochemical evidence for hybrid sialoglyco-proteins of human erythrocytes

Abstract

The 2 major sialoglycoproteins of the human erythrocyte membrane (.alpha. and .delta., glycophorins A and B) have identical amino acid sequences for the first 26 residues from the amino terminus, except that .alpha. expresses M or N blood group antigen activity whereas .delta. carries only blood group N activity. The asparagine at position 26 on .alpha. carries an oligosaccharide chain which is absent from the same position on .delta.. The 2 sialoglycoproteins differ in their remaining amino acid sequence and .delta. expresses blood group Ss activity. There are also variant sialoglycoproteins which have properties of both the .alpha. and .delta. molecules and may be hybrids of these. Antibodies directed against different structural regions of the major sialoglycoprotein .alpha. were used to show that 2 variant erythrocytes (Miltenberger class V (MiV) and Ph) contain hybrid sialoglycoprotein molecules. These hybrid sialoglycoproteins arise from cross-over events between the genes coding for .alpha. and .delta.. The 2 genes are probably closely associated in the order .alpha., .delta. (5'' .fwdarw. 3'') on the chromosome.