Title : Membrane glycophorins in
Sta blood group erythrocytes
Abstract :
- Structural and immunochemical studies of glycophorins isolated from erythrocytes of an individual homozygous for the M Sta blood group phenotype are described
- Reactivities with specific monoclonal antibodies indicated that two major M and N glycophorins were present
- The M and N Sta glycophorins were resolved by Lens culinaris lectin affinity chromatography
- The N species was not held on the lectin but the M species, like control alpha glycophorins, was retained and could be eluted with alpha-methylmannoside
- The two proteins were present in almost equimolar amounts
- Studies of the CNBr fragments provided evidence that the structure of M Sta glycophorin is the same as that of the usual M alpha glycophorin but that the N Sta glycophorin is a variant
- The amino-terminal octapeptides of the M and N species were similar in amino acid and carbohydrate composition to those isolated, respectively, from M and N alpha glycophorins
- The studies focused on CNBr glycopeptide B that, in control alpha glycophorins, extends from amino acid residues 9 to 81
- The fragment from the M species exhibited properties identical to those of the corresponding fragment of control alpha glycophorins in terms of size, chromatographic behavior, amino acid and carbohydrate contents and com positions, the presence of O-glycosidically linked saccharides and a single Asn-linked carbohydrate unit. Asn-linked carbohydrate unit
- The structures of the O-linked units were inferred experimentally to be NeuAc(alpha 2,3)Gal-(beta 1,3)GalNAc and NeuAc(alpha 2,3)Gal(beta 1,3) [NeuAc(alpha 2,6)]GalNAc, present in a ratio similar to that found in controls; and the Asn-linked unit Asn-linked unit also appeared to be as in the control
- The tryptic glycopeptide pattern of the M Sta glycophorin CNBr fragment B was identical to the pattern of the corresponding control fragment , and the com position of the tryptic peptides suggested sequence identity with the control fragment
- In contrast, the N Sta glycophorin yielded two CNBr glycopeptides B; both contained fewer amino acid residues and virtually lacked Man and GlcNAc, indicating the absence of the Asn-linked carbohydrate Asn-linked carbohydrate
- The much decreased levels of these carbohydrates in the intact N protein , corroborated the latter finding
- The O-glycosidic saccharides appeared similar to those found in control alpha glycophorins
- However, the tryptic glycopeptide pattern of the variant differed from control M or N alpha glycophorins, suggesting a deletion of a large segment of the molecule near residues 40-61 and/or a substitution of methionine for a residue upstream from residue 40
- (ABSTRACT TRUNCATED AT 400 WORDS