Characterization of mucin-type core-1 beta1-3 galactosyltransferase homologous enzymes in Drosophila melanogaster.
Mucin type O-glycosylation is a widespread modification of eukaryotic proteins. The transfer of N-acetylgalactosamine to selected serine or threonine residues is catalyzed by a family of polypeptide N-acetylgalactosaminyltransferases localized in the Golgi apparatus. The most abundant elongation of O-glycans is the addition of a beta1-3 linked galactose by the core-1 beta1-3 galactosyltransferase (core-1 beta3GalT), thereby building the T-antigen or core-1 structure Gal(beta1-3)GalNAc(alpha1-O). We have isolated four Drosophila melanogaster cDNAs encoding proteins structurally similar to the human core-1 beta3GalT enzyme and expressed them as FLAG-tagged proteins in Sf9 insect cells. The identity of these D. melanogasterbeta3GalT enzymes with a core-1 beta3GalT activity was confirmed by utilization of MUC5AC mucin derived O-glycopeptide acceptors. In addition to the core-1 beta3GalT activity toward O-glycoprotein substrates, one member of this enzyme family showed a strong activity towards glycolipid acceptors, thereby building the core-1 terminated Nz6 glycosphingolipid. Transcripts of the embryonically expressed core-1 beta3GalTs were found in the maternally deposited mRNA, in salivary glands and in the amnioserosa. The presence of multiple core-1 beta3GalT genes in D. melanogaster suggests an increased complexity of core-1 O-glycan expression, which is possibly related to multiple developmental and physiological functions attributable to this class of glycans.
Müller
Reto
R
Institute of Physiology, University of Zürich, Switzerland.
Hülsmeier
Andreas J
AJ
Altmann
Friedrich
F
Ten Hagen
Kelly
K
Tiemeyer
Michael
M
Hennet
Thierry
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D018076:DNA, Complementary / Q000235:genetics; D004331:Drosophila melanogaster / Q000196:embryology / Q000201:enzymology* / Q000235:genetics; D005700:Galactosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D017344:Genes, Insect; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D013379:Substrate Specificity
D018076:DNA, Complementary; D012333:RNA, Messenger; D011994:Recombinant Proteins; D005700:Galactosyltransferases; C076385:glycoprotein-N-acetylgalactosamine 3-beta-galactosyltransferase