title: Immobilization antigens from Tetrahymena thermophila are glycosyl-phosphatidylinositol-linked proteins.
abstract: We have studied four strains of Tetrahymena thermophila, each of which expresses a different allele of the SerH gene and produces a distinctive surface protein of the immobilization antigen (i-antigen) class. Following exposure of the strains to [3H]ethanolamine or [3H]myristic acid, a protein corresponding in molecular mass to the characteristic i-antigen for that strain became highly labeled, as determined by mobility in sodium dodecylsulfate-polyacrylamide electrophoresis gels. Furthermore, antibodies raised to the i-antigens of the T. thermophila strains selectively immunoprecipitated radioactive proteins having molecular mass identical to that of the i-antigen characteristic for that particular strain. The lipid moieties labeled by [3H]myristate were not susceptible to hydrolysis by exogenous phosphatidylinositol-specific phospholipase C from bacteria. However, when protein extraction was carried out in the absence of phospholipase C inhibitors, radioactive fatty acids derived from [3H]myristate were rapidly cleaved from the putative i-antigens. On the basis of available data, it was concluded that T. thermophila i-antigens contain covalently-linked glycosyl-phosphatidylinositol anchors.
authors.affiliation: Department of Botany, University of Texas, Austin 78713.
authors.forename: Y G
authors.initials: YG
authors.lastname: Ko
authors.forename: G A
authors.initials: GA
authors.lastname: Thompson
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000737:chemistry*; D000954:Antigens, Surface / Q000737:chemistry* / Q000276:immunology; D019856:Ethanolamine; D004983:Ethanolamines / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000032:analysis*; D019814:Myristic Acid; D009227:Myristic Acids / Q000378:metabolism; D015800:Protozoan Proteins / Q000032:analysis; D016808:Tetrahymena thermophila / Q000737:chemistry* / Q000276:immunology; D010738:Type C Phospholipases / Q000494:pharmacology
chemical_list: D000953:Antigens, Protozoan; D000954:Antigens, Surface; D004983:Ethanolamines; D017261:Glycosylphosphatidylinositols; D009227:Myristic Acids; D015800:Protozoan Proteins; C043323:immobilization antigens; D019814:Myristic Acid; D019856:Ethanolamine; D010738:Type C Phospholipases