title: Biochemical correlation of activity of the α-dystroglycan-modifying glycosyltransferase POMGnT1 with mutations in muscle-eye-brain disease.
abstract: Congenital muscular dystrophies have a broad spectrum of genotypes and phenotypes and there is a need for a better biochemical understanding of this group of diseases in order to aid diagnosis and treatment. Several mutations resulting in these diseases cause reduced O-mannosyl glycosylation of glycoproteins, including α-dystroglycan. The enzyme POMGnT1 (protein-O-mannose N-acetylglucosaminyltransferase 1; EC 2.4.1.-) catalyses the transfer of N-acetylglucosamine to O-linked mannose of α-dystroglycan. In the present paper we describe the biochemical characterization of 14 clinical mutants of the glycosyltransferase POMGnT1, which have been linked to muscle-eye-brain disease or similar conditions. Truncated mutant variants of the human enzyme (recombinant POMGnT1) were expressed in Escherichia coli and screened for catalytic activity. We find that three mutants show some activity towards mannosylated peptide substrates mimicking α-dystroglycan; the residues affected by these mutants are predicted by homology modelling to be on the periphery of the POMGnT1 surface. Only in part does the location of a previously described mutated residue on the periphery of the protein structure correlate with a less severe disease mutant.
authors.affiliation: Manchester Interdisciplinary Biocentre, University of Manchester, Manchester M1 7ND, UK.
authors.forename: Josef
authors.initials: J
authors.lastname: Voglmeir
authors.forename: Sara
authors.initials: S
authors.lastname: Kaloo
authors.forename: Nicolas
authors.initials: N
authors.lastname: Laurent
authors.forename: Marco M
authors.initials: MM
authors.lastname: Meloni
authors.forename: Lisa
authors.initials: L
authors.lastname: Bohlmann
authors.forename: Iain B H
authors.initials: IB
authors.lastname: Wilson
authors.forename: Sabine L
authors.initials: SL
authors.lastname: Flitsch
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D049030:Dystroglycans / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D016695:Glycosyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007223:Infant; D008297:Male; D009154:Mutation / Q000235:genetics*; D017351:N-Acetylglucosaminyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D013379:Substrate Specificity; D058494:Walker-Warburg Syndrome / Q000235:genetics / Q000378:metabolism; D055815:Young Adult
chemical_list: C483081:DAG1 protein, human; D010446:Peptide Fragments; D049030:Dystroglycans; D016695:Glycosyltransferases; D017351:N-Acetylglucosaminyltransferases; C443106:protein O-mannose beta-1,2-N-acetylglucosaminyltransferase