title: Human red cell aquaporin CHIP. I. Molecular characterization of ABH and Colton blood group antigens.
abstract: Blood group antigens are structural variants in surface carbohydrate or amino acid polymorphisms on extracellular domains of membrane proteins. The red cell water channel-forming integral protein (Aquaporin CHIP) is a homotetramer with only one N-glycosylated subunit, however no CHIP-associated blood group antigens have yet been identified. Immunoblotting, monosaccharide composition analysis, and selective glycosidase digestions revealed that the CHIP-associated oligosaccharide contains ABH determinants and resembles a band 3-type glycan that cannot be cleaved from intact membranes by Peptide:N-glycosidase F. The molecular structure of the Colton antigens was previously unknown, but CHIP was selectively immunoprecipitated with anti-Coa or anti-Co(b). The DNA sequence from Colton-typed individuals predicted that residue 45 is alanine in the Co(a+b-) phenotype and valine in the Co(a-b+) phenotype. The nucleotide polymorphism corresponds to a PflMI endonuclease digestion site in the DNA from Co(a-b+) individuals. These studies have defined antigens within two blood group systems on CHIP: (a) an ABH-bearing polylactosaminoglycan attached to a poorly accessible site in the native membrane; and (b) the Colton antigen polymorphism which may permit the identification of rare individuals with defective water channel expression.
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2185.
authors.forename: B L
authors.initials: BL
authors.lastname: Smith
authors.forename: G M
authors.initials: GM
authors.lastname: Preston
authors.forename: F A
authors.initials: FA
authors.lastname: Spring
authors.forename: D J
authors.initials: DJ
authors.lastname: Anstee
authors.forename: P
authors.initials: P
authors.lastname: Agre
mesh_terms: D000017:ABO Blood-Group System / Q000097:blood / Q000737:chemistry*; D051398:Aquaporin 1; D020346:Aquaporins; D001483:Base Sequence; D001789:Blood Group Antigens; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002460:Cell Line; D017931:DNA Primers; D004910:Erythrocyte Membrane / Q000737:chemistry*; D005091:Exons; D006801:Humans; D007473:Ion Channels / Q000097:blood* / Q000737:chemistry* / Q000235:genetics; D008214:Lymphocytes / Q000378:metabolism; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000032:analysis; D009844:Oligosaccharides / Q000737:chemistry*; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D017433:Protein Structure, Secondary; D015183:Restriction Mapping
chemical_list: D000017:ABO Blood-Group System; C496020:AQP1 protein, human; D020346:Aquaporins; D001789:Blood Group Antigens; D017931:DNA Primers; D007473:Ion Channels; D046911:Macromolecular Substances; D009005:Monosaccharides; D009844:Oligosaccharides; D051398:Aquaporin 1