title: The dTDP-4-dehydro-6-deoxyglucose reductase encoding fcd gene is part of the surface layer glycoprotein glycosylation gene cluster of Geobacillus tepidamans GS5-97T.
abstract: The glycan chain of the S-layer protein of Geobacillus tepidamans GS5-97(T) consists of disaccharide repeating units composed of L-rhamnose and D-fucose, the latter being a rare constituent of prokaryotic glycoconjugates. Although biosynthesis of nucleotide-activated L-rhamnose is well established, D-fucose biosynthesis is less investigated. The conversion of alpha-D-glucose-1-phosphate into thymidine diphosphate (dTDP)-4-dehydro-6-deoxyglucose by the sequential action of RmlA (glucose-1-phosphate thymidylyltransferase) and RmlB (dTDP-glucose-4,6-dehydratase) is shared between the dTDP-D-fucose and the dTDP-L-rhamnose biosynthesis pathway. This key intermediate is processed by the dTDP-4-dehydro-6-deoxyglucose reductase Fcd to form dTDP-alpha-D-fucose. We identified the fcd gene in G. tepidamans GS5-97(T) by chromosome walking and performed functional characterization of the recombinant 308-amino acid enzyme. The in vitro activity of the enzymatic cascade (RmlB and Fcd) was monitored by high-performance liquid chromatography and the reaction product was confirmed by (1)H and (13)C nuclear magnetic resonance spectroscopy. This is the first characterization of the dTDP-alpha-D-fucopyranose biosynthesis pathway in a Gram-positive organism. fcd was identified as 1 of 20 open reading frames contained in a 17471-bp S-layer glycosylation (slg) gene cluster on the chromosome of G. tepidamans GS5-97(T). The sgtA structural gene is located immediately upstream of the slg gene cluster with an intergenic region of 247 nucleotides. By comparison of the SgtA amino acid sequence with the known glycosylation pattern of the S-layer protein SgsE of Geobacillus stearothermophilus NRS 2004/3a, two out of the proposed three glycosylation sites on SgtA could be identified by electrospray ionization quadrupole-time-of-flight mass spectrometry to be at positions Ser-792 and Thr-583.
authors.affiliation: Zentrum für NanoBiotechnologie, Universität für Bodenkultur Wien, A-1190 Vienna, Austria.
authors.forename: Sonja
authors.initials: S
authors.lastname: Zayni
authors.forename: Kerstin
authors.initials: K
authors.lastname: Steiner
authors.forename: Andreas
authors.initials: A
authors.lastname: Pföstl
authors.forename: Andreas
authors.initials: A
authors.lastname: Hofinger
authors.forename: Paul
authors.initials: P
authors.lastname: Kosma
authors.forename: Christina
authors.initials: C
authors.lastname: Schäffer
authors.forename: Paul
authors.initials: P
authors.lastname: Messner
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D016384:Consensus Sequence; D045302:Geobacter / Q000201:enzymology* / Q000235:genetics*; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008562:Membrane Glycoproteins / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D016366:Open Reading Frames; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013401:Sugar Alcohol Dehydrogenases / Q000737:chemistry / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D008562:Membrane Glycoproteins; C055764:S-layer proteins; D013401:Sugar Alcohol Dehydrogenases; C520610:dTDP-4-dehydro-6-deoxyglucose reductase, Geobacillus tepidamans