title: Different roles of the two components of human protein O-mannosyltransferase, POMT1 and POMT2.
abstract: Protein O-mannosyltransferase 1 (POMT1) and its homolog, POMT2, are responsible for the catalysis of the first step in O-mannosyl glycan synthesis. Mutations in their genes are associated with a type of congenital muscular dystrophy called Walker-Warburg syndrome. Arg(64), Glu(78) and Arg(138) in the N-terminus region of ScPmt1p, a POMT homolog in Saccharomyces cerevisiae, are important for transferase activity. Arg(138) is also essential for complex formation with ScPmt2p. Here we examined the effects of replacing the corresponding residues in human POMT1 and POMT2 with Ala on complex formation and enzymatic activity. The human POMT1 mutants lost almost all transferase activity while the POMT2 mutants retained enzymatic activity. Neither mutant lost its ability to form complexes with the native counter component. These results indicate that ScPmtps and human POMTs have different mechanisms of complex formation. They also suggest that human POMT1 and POMT2 have discrete functions since the effect of amino acid substitutions on enzymatic activity are different.
authors.affiliation: Molecular Glycobiology, Research Team for Mechanism of Aging, Tokyo Metropolitan Institute of Gerontology, Foundation for Research on Aging and Promotion of Human Welfare, Itabashi-ku, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Akasaka-Manya
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Manya
authors.forename: Masami
authors.initials: M
authors.lastname: Hayashi
authors.forename: Tamao
authors.initials: T
authors.lastname: Endo
mesh_terms: D000409:Alanine / Q000737:chemistry / Q000235:genetics; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001120:Arginine / Q000737:chemistry* / Q000235:genetics; D018698:Glutamic Acid / Q000737:chemistry* / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D008364:Mannosyltransferases / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D018698:Glutamic Acid; D001120:Arginine; D008364:Mannosyltransferases; C082696:protein O-mannosyltransferase; D000409:Alanine