Localization of an O-glycosylation site in the alpha-subunit of the human platelet integrin GPIIb/IIIa involved in Baka (HPA-3a) alloantigen expression.
The human alloantigen system Baka/b is associated with a Ile843-->Ser replacement on platelet glycoprotein IIb, the alpha-subunit of the integrin receptor for fibrinogen (GPIIb/IIIa). Recent immunological studies indicate that sialylated oligosaccharide chain(s) are also implicated in expression of the Baka determinant. Here we show that the GPIIb fragment 704-856 contains the whole Baka epitope, and that chemical cleavage of a single O-linked oligosaccharide chain within this GPIIb domain correlates with the loss of its anti-Baka antibodies binding ability. Ser847 was identified as the O-glycosylation site. Therefore, our results show that the Ser847 modification is responsible for the expression of the GPIIb-specific Baka alloantigen, and provide thus a link between the molecular biology and the immunologic observations.
Calvete
J J
JJ
Instituto de Química-Física CSIC, Madrid, Spain.
Muñiz-Diaz
E
E
D000595:Amino Acid Sequence; D016824:Antigens, Human Platelet / Q000737:chemistry* / Q000276:immunology; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D006031:Glycosylation; D006801:Humans; D007519:Isoantigens / Q000032:analysis*; D008969:Molecular Sequence Data; D010980:Platelet Membrane Glycoproteins / Q000737:chemistry*; D012694:Serine / Q000737:chemistry*
C044561:3a alloantigen, human; D016824:Antigens, Human Platelet; D000939:Epitopes; D007519:Isoantigens; D010980:Platelet Membrane Glycoproteins; D012694:Serine