title: B-transferase with a Pro234Ser substitution acquires AB-transferase activity.
abstract: A/B-Transferase is a glycosyltransferase that transfers a sugar substrate onto H-antigen, which is responsible for the synthesis of glycoprotein- and glycolipid-conjugates termed A/B-antigens. One polymorphism that causes the Pro234Ser substitution in B-transferase was recently found in a genotyping study, and might be cis-AB. In the present study, we analyzed the phenotypes arising from the enzymatic specificity of B-transferase with the Pro234Ser mutation. To evaluate the effect of the P234S mutation on enzymatic specificity, we generated an expression plasmid for B-transferase with Pro234Ser as well as A-transferase with Leu266Met, which is frequently found in cis-ABs. Transfection of B-transferase/P234S or A-transferase/L266M cDNA into HeLa cells, an O-blood group cell line, resulted in an AB-phenotype by absorption-elution testing and immunostaining, whereas A- and B-transferase-expressing HeLa cells exhibited only their own activity. Molecular simulation indicated that the P234S mutation causes a conformational change in the substrate pocket making it suitable for N-acetylgalactosamine.
authors.affiliation: Atopy (Allergy) Research Center, Juntendo University School of Medicine, Hongo, Bunkyo-ku, Tokyo, Japan. chinishi@juntendo.ac.jp
authors.forename: Chiyomi
authors.initials: C
authors.lastname: Nishida
authors.forename: Takeo
authors.initials: T
authors.lastname: Tomita
authors.forename: Makoto
authors.initials: M
authors.lastname: Nishiyama
authors.forename: Ryuyo
authors.initials: R
authors.lastname: Suzuki
authors.forename: Mutsuko
authors.initials: M
authors.lastname: Hara
authors.forename: Yukio
authors.initials: Y
authors.lastname: Itoh
authors.forename: Hideoki
authors.initials: H
authors.lastname: Ogawa
authors.forename: Ko
authors.initials: K
authors.lastname: Okumura
authors.forename: Chiharu
authors.initials: C
authors.lastname: Nishiyama
mesh_terms: D000017:ABO Blood-Group System / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D000116:Acetylgalactosamine / Q000378:metabolism*; D002846:Chromatography, Affinity; D005260:Female; D005838:Genotype; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D056004:Molecular Dynamics Simulation; D009154:Mutation; D017350:N-Acetylgalactosaminyltransferases / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D010641:Phenotype; D010957:Plasmids; D011110:Polymorphism, Genetic / Q000276:immunology*; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D014162:Transfection
chemical_list: D000017:ABO Blood-Group System; D017350:N-Acetylgalactosaminyltransferases; D000116:Acetylgalactosamine