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2 results on '"Birgit, Keck"'

1. The Drosophila gene brainiac encodes a glycosyltransferase putatively involved in glycosphingolipid synthesis

Author

Stephen M. Cohen, Mark R. Stroud, Johannes W. Pedersen, Mads A. Jensen, Henrik Clausen, Steven B. Levery, Tilo Schwientek, Hans H. Wandall, Margarida Amado, and Birgit Keck

Subjects
DNA, Complementary, Magnetic Resonance Spectroscopy, Glycoside Hydrolases, Mannose, Genes, Insect, Disaccharides, Biochemistry, Glycosphingolipids, Uridine Diphosphate, Cell Line, Substrate Specificity, chemistry.chemical_compound, Glycolipid, Notch Family, Complementary DNA, Glycosyltransferase, Animals, Drosophila Proteins, Glycoside hydrolase, Molecular Biology, Gene, Chromatography, High Pressure Liquid, Phylogeny, biology, Dose-Response Relationship, Drug, Glycosyltransferases, Membrane Proteins, Cell Biology, carbohydrates (lipids), Kinetics, chemistry, Databases as Topic, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Mutation, biology.protein, lipids (amino acids, peptides, and proteins), Drosophila, Baculoviridae, Drosophila Protein
Abstract

The Drosophila genes fringe and brainiac exhibit sequence similarities to glycosyltransferases. Drosophila and mammalian fringe homologs encode UDP-N-acetylglucosamine:fucose-O-Ser beta1,3-N-acetylglucosaminyltransferases that modulate the function of Notch family receptors. The biological function of brainiac is less well understood. brainiac is a member of a large homologous mammalian beta3-glycosyltransferase family with diverse functions. Eleven distinct mammalian homologs have been demonstrated to encode functional enzymes forming beta1-3 glycosidic linkages with different UDP donor sugars and acceptor sugars. The putative mammalian homologs with highest sequence similarity to brainiac encode UDP-N-acetylglucosamine:beta1,3-N-acetylglucosaminyltransferases (beta3GlcNAc-transferases), and in the present study we show that brainiac also encodes a beta3GlcNAc-transferase that uses beta-linked mannose as well as beta-linked galactose as acceptor sugars. The inner disaccharide core structures of glycosphingolipids in mammals (Galbeta1-4Glcbeta1-Cer) and insects (Manbeta1-4Glcbeta1-Cer) are different. Both disaccharide glycolipids served as substrates for brainiac, but glycolipids of insect cells have so far only been found to be based on the GlcNAcbeta1-3Manbeta1-4Glcbeta1-Cer core structure. Infection of High Five(TM) cells with baculovirus containing full coding brainiac cDNA markedly increased the ratio of GlcNAcbeta1-3Manbeta1-4Glcbeta1-Cer glycolipids compared with Galbeta1-4Manbeta1-4Glcbeta1-Cer found in wild type cells. We suggest that brainiac exerts its biological functions by regulating biosynthesis of glycosphingolipids.

Published
2002

2. Functional conservation of subfamilies of putative UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltransferases in Drosophila, Caenorhabditis elegans, and mammals. One subfamily composed of l(2)35Aa is essential in Drosophila

Author

Tilo, Schwientek, Eric P, Bennett, Carlos, Flores, John, Thacker, Martin, Hollmann, Celso A, Reis, Jane, Behrens, Ulla, Mandel, Birgit, Keck, Mireille A, Schäfer, Kim, Haselmann, Roman, Zubarev, Peter, Roepstorff, Joy M, Burchell, Joyce, Taylor-Papadimitriou, Michael A, Hollingsworth, and Henrik, Clausen

Subjects
Male, Molecular Sequence Data, Cell Line, Evolution, Molecular, Mice, Catalytic Domain, Animals, Humans, Protein Isoforms, Tissue Distribution, Amino Acid Sequence, Cloning, Molecular, Caenorhabditis elegans, Alleles, Conserved Sequence, In Situ Hybridization, Phylogeny, Genome, Base Sequence, Models, Genetic, Sequence Homology, Amino Acid, Ovary, Blotting, Northern, Protein Structure, Tertiary, Drosophila melanogaster, Phenotype, Microscopy, Fluorescence, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, N-Acetylgalactosaminyltransferases, Female, Peptides
Abstract

The completed fruit fly genome was found to contain up to 15 putative UDP-N-acetyl-alpha-d-galactosamine:polypeptide N-acetylgalactosaminyltransferase (GalNAc-transferase) genes. Phylogenetic analysis of the putative catalytic domains of the large GalNAc-transferase enzyme families of Drosophila melanogaster (13 available), Caenorhabditis elegans (9 genes), and mammals (12 genes) indicated that distinct subfamilies of orthologous genes are conserved in each species. In support of this hypothesis, we provide evidence that distinctive functional properties of Drosophila and human GalNAc-transferase isoforms were exhibited by evolutionarily conserved members of two subfamilies (dGalNAc-T1 (l(2)35Aa) and GalNAc-T11; dGalNAc-T2 (CG6394) and GalNAc-T7). dGalNAc-T1 and novel human GalNAc-T11 were shown to encode functional GalNAc-transferases with the same polypeptide acceptor substrate specificity, and dGalNAc-T2 was shown to encode a GalNAc-transferase with similar GalNAc glycopeptide substrate specificity as GalNAc-T7. Previous data suggested that the putative GalNAc-transferase encoded by l(2)35Aa had a lethal phenotype (Flores, C., and Engels, W. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 2964-2969), and this was substantiated by sequencing of three lethal alleles l(2)35Aa(HG8), l(2)35Aa(SF12), and l(2)35Aa(SF32). The finding that subfamilies of GalNAc-transferases with distinct catalytic functions are evolutionarily conserved stresses that GalNAc-transferase isoforms may serve unique biological functions rather than providing functional redundancy, and this is further supported by the lethal phenotype of l(2)35Aa.

Published
2002

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