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Found 1 structure.
Displayed structure 1
| a-D-Glcp-(1-P | Show graphically |
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Structure type: monomer
Trivial name: α-D-glucose-1-phosphate
Contained glycoepitopes: IEDB_142488,IEDB_144998,IEDB_145002,IEDB_146664,IEDB_983931,SB_192
O antigen variation due to the presence of different types of sugars and sugar linkages is important for the survival of bacteria against host immune systems. The O antigens of S. dysenteriae type 7 and E. coli O7 contain 4-(N-acetylglycyl)amino-4,6-dideoxy-D-glucose (D-Qui4NGlyAc) and 4-acetamido-4,6-dideoxy-D-glucose (D-Qui4NAc), respectively, which are sugars not often found in studied polysaccharides. In this study, we characterized the biosynthetic pathways for dTDP-D-Qui4N and dTDP-D-Qui4NAc (the nucleotide-activated precursors of D-Qui4NGlyAc and D-Qui4NAc in O antigens). Predicted genes involved in the synthesis of the two sugars were cloned, and the gene products were overexpressed and purified as His-tagged fusion proteins. In vitro enzymatic reactions were carried out using the purified proteins, and the reaction products were analyzed by capillary electrophoresis, electrospray ionization mass spectrometry, and nuclear magnetic resonance spectroscopy. It was shown that in S. dysenteriae type 7 and E. coli O7 dTDP-D-Qui4N is synthesized from α-D-glucose-1-phosphate in three reaction steps catalyzed by glucose-1-phosphate thymidyltransferase (RmlA), dTDP-D-glucose 4,6-dehydratase (RmlB), and dTDP-4-keto-6-deoxy-D-glucose aminotransferase (VioA), respectively. An additional acetyltransferase (VioB) catalyzes the conversion of dTDP-D-Qui4N into dTDP-D-Qui4NAc in E. coli O7. Kinetic parameters and some other properties of VioA and VioB are described and differences between VioA proteins from S. dysenteriae type 7 and E. coli O7 discussed. To our knowledge, this is the first time that functions of VioA and VioB have been biochemically characterized. This study provides valuable enzyme sources for the production of dTDP-D-Qui4N and dTDP-D-Qui4NAc, which are potentially useful in pharmaceutical industry for drugs development
biosynthesis, Escherichia coli, Shigella dysenteriaes
NCBI PubMed ID: 17905981This review covers the O antigens of the 46 serotypes of Shigella, but those of most Shigella flexneri are variants of one basic structure, leaving 34 Shigella distinct O antigens to review, together with their gene clusters. Several of the structures and gene clusters are reported for the first time and this is the first such group for which structures and DNA sequences have been determined for all O antigens. Shigella strains are in effect Escherichia coli with a specific mode of pathogenicity, and 18 of the 34 O antigens are also found in traditional E. coli. Three are very similar to E. coli O antigens and 13 are unique to Shigella strains. The O antigen of Shigella sonnei is quite atypical for E. coli and is thought to have transferred from Plesiomonas. The other 12 O antigens unique to Shigella strains have structures that are typical of E. coli, but there are considerably more anomalies in their gene clusters, probably reflecting recent modification of the structures. Having the complete set of structures and genes opens the way for experimental studies on the role of this diversity in pathogenicity.
structure, O antigen, Shigella, O antigen gene cluster, O antigen diversity
NCBI PubMed ID: 18422615Derivatives of 3-amino-3,6-dideoxyhexoses are widespread in Nature. They are part of the repeating units of lipopolysaccharide O-antigens, of the glycan moiety of S-layer (bacterial cell surface layer) glycoproteins and also of many antibiotics. In the present study, we focused on the elucidation of the biosynthesis pathway of dTDP-α-D-Quip3NAc (dTDP-3-acetamido-3,6-dideoxy-α-D-glucose) from the Gram-positive, anaerobic, thermophilic organism Thermoanaerobacterium thermosaccharolyticum E207-71, which carries Quip3NAc in its S-layer glycan. The biosynthesis of dTDP-α-D-Quip3NAc involves five enzymes, namely a transferase, a dehydratase, an isomerase, a transaminase and a transacetylase, and follows a pathway similar to that of dTDP-α-D-Fucp3NAc (dTDP-3-acetamido-3,6-dideoxy-α-D-galactose) biosynthesis in Aneurinibacillus thermoaerophilus L420-91(T). The ORFs (open reading frames) of interest were cloned, overexpressed in Escherichia coli and purified. To elucidate the enzymatic cascade, the different products were purified by HPLC and characterized by NMR spectroscopy. The initiating reactions catalysed by the glucose-1-phosphate thymidylyltransferase RmlA and the dTDP-D-glucose-4,6-dehydratase RmlB are well established. The subsequent isomerase was shown to be capable of forming a dTDP-3-oxo-6-deoxy-D-glucose intermediate from the RmlB product dTDP-4-oxo-6-deoxy-D-glucose, whereas the isomerase involved in the dTDP-α-D-Fucp3NAc pathway synthesizes dTDP-3-oxo-6-deoxy-D-galactose. The subsequent reaction steps of either pathway involve a transaminase and a transacetylase, leading to the specific production of nucleotide-activated 3-acetamido-3,6-dideoxy-α-D-glucose and 3-acetamido-3,6-dideoxy-α-D-galactose respectively. Sequence comparison of the ORFs responsible for the biosynthesis of dTDP-α-D-Quip3NAc revealed homologues in Gram-negative as well as in antibiotic-producing Gram-positive bacteria. There is strong evidence that the elucidated biosynthesis pathway may also be valid for LPS (lipopolysaccharide) O-antigen structures and antibiotic precursors
3, 6-dideoxyhexose, 3-amino-3, bacterial cell surface layer (S-layer) glycoprotein, dTDP-3-acetamido-3, 6-dideoxy-a-D-glucose (dTDP-a-D-Quip3NAc), 4-oxoisomerase, nucleotide-activated sugar precursor, Thermoanaerobacterium thermosaccharolyticum
NCBI PubMed ID: 17941826D-Fucofuranose (D-Fucf) is a component of Escherichia coli O52 O antigen. This uncommon sugar is also the sugar moiety of the anticancer drug - gilvocarcin V produced by many streptomycetes. In E. coli O52, rmlA, rmlB, fcf1 and fcf2 were proposed in a previous study by our group to encode the enzymes of the dTDP-d-Fucf (the nucleotide-activated form of d-Fucf) biosynthetic pathway. In this study, Fcf1 and Fcf2 from E. coli O52 were expressed, purified and assayed for their respective activities. Novel product peaks from enzyme-substrate reactions were detected by capillary electrophoresis and the structures of the product compounds were elucidated by electro-spray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. Fcf1 was confirmed to be a dTDP-6-deoxy-d-xylo-hex-4-ulopyranose reductase for the conversion of dTDP-6-deoxy-d-xylo-hex-4-ulopyranose to dTDP-d-fucopyranose (dTDP-D-Fucp), and Fcf2 a dTDP-d-Fucp mutase for the conversion of dTDP-d-Fucp to dTDP-d-Fucf. The Km of Fcf1 for dTDP-6-deoxy-d-xylo-hex-4-ulopyranose was determined to be 0.38 mM, and of Fcf2 for dTDP-d-Fucp to be 3.43 mM. The functional role of fcf1 and fcf2 in the biosynthesis of E. coli O52 O antigen were confirmed by mutation and complementation tests. This is the first time that the biosynthetic pathway of dTDP-d-Fucf has been fully characterized.
biosynthesis, O antigen, Biosynthetic Pathways, Escherichia coli O52, D-Fucofuranose (D-Fucf)
NCBI PubMed ID: 19019146| New query | Export IDs | Home | Help |
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