title: Genetic and structural characterization of an amino acid dimorphism in glycoprotein Ib alpha involved in platelet transfusion refractoriness.
abstract: The platelet-specific alloantigen, Siba, located within the alpha-subunit of the glycoprotein (GP) Ib-IX membrane receptor, has been found to be involved in the pathogenesis of platelet transfusion refractoriness. We have identified the existence of a naturally occurring threonine/methionine dimorphism at position 145 of the GPIb alpha sequence, and determined that the Siba antigen corresponds to the molecule containing methionine145. The diallelic codons can be detected by restriction enzyme analysis of amplified genomic DNA fragments from the GPIb alpha gene. Evaluation of 61 healthy blood donors showed that the allele frequencies are 89% and 11% for the threonine145 and methionine145 codons, respectively. A positive correlation exists between platelet reactivity with the anti-Siba antibody and the presence of a methionine145-encoding allele. Moreover, recombinant expression of two soluble GPIb alpha fragments differing only at residue 145, provided definitive evidence that the human anti-Siba antibody reacts only with the molecule containing methionine145. These results explain the structural basis of the Siba human alloantigen system and define screening methodologies useful in transfusion medicine to match donor and recipient platelets accordingly.
authors.affiliation: Department of Molecular and Experimental Medicine/Committee on Vascular Biology, Scripps Research Institute, La Jolla, CA 92037.
authors.forename: M
authors.initials: M
authors.lastname: Murata
authors.forename: K
authors.initials: K
authors.lastname: Furihata
authors.forename: F
authors.initials: F
authors.lastname: Ishida
authors.forename: S R
authors.initials: SR
authors.lastname: Russell
authors.forename: J
authors.initials: J
authors.lastname: Ware
authors.forename: Z M
authors.initials: ZM
authors.lastname: Ruggeri
mesh_terms: D000596:Amino Acids / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D000941:Antigens / Q000737:chemistry / Q000276:immunology; D016824:Antigens, Human Platelet / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D001483:Base Sequence; D016913:Blood Component Transfusion; D001792:Blood Platelets / Q000276:immunology*; D003062:Codon; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D008715:Methionine / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D008969:Molecular Sequence Data; D010980:Platelet Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D013912:Threonine / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D014162:Transfection
chemical_list: D000596:Amino Acids; D000941:Antigens; D016824:Antigens, Human Platelet; D003062:Codon; D010980:Platelet Membrane Glycoproteins; D011994:Recombinant Proteins; D013912:Threonine; D008715:Methionine