Taxonomic group: bacteria / Proteobacteria
(Phylum: Proteobacteria)
Associated disease: infection due to Escherichia coli [ICD11:
XN6P4 
]
NCBI PubMed ID: 14729696Journal NLM ID: 2985120RPublisher: American Society for Microbiology
Correspondence: wvann
helix.nih.gov
Institutions: Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, USA
The K1 capsule is an essential virulence determinant of Escherichia coli strains that cause meningitis in neonates. Biosynthesis and transport of the capsule, an α-2,8-linked polymer of sialic acid, are encoded by the 17-kb kps gene cluster. We deleted neuC, a K1 gene implicated in sialic acid synthesis, from the chromosome of EV36, a K-12-K1 hybrid, by allelic exchange. Exogenously added sialic acid restored capsule expression to the deletion strain (∆neuC), confirming that NeuC is necessary for sialic acid synthesis. The deduced amino acid sequence of NeuC showed similarities to those of UDP-N-acetylglucosamine (GlcNAc) 2-epimerases from both prokaryotes and eukaryotes. The NeuC homologue from serotype III Streptococcus agalactiae complements ∆neuC. We cloned the neuC gene into an intein expression vector to facilitate purification. We demonstrated by paper chromatography that the purified neuC gene product catalyzed the formation of [2-(14)C]acetamidoglucal and [N-(14)C]acetylmannosamine (ManNAc) from UDP-[(14)C]GlcNAc. The formation of reaction intermediate 2-acetamidoglucal with the concomitant release of UDP was confirmed by proton and phosphorus nuclear magnetic resonance spectroscopy. NeuC could not use GlcNAc as a substrate. These data suggest that neuC encodes an epimerase that catalyzes the formation of ManNAc from UDP-GlcNAc via a 2-acetamidoglucal intermediate. The unexpected release of the glucal intermediate and the extremely low rate of ManNAc formation likely were a result of the in vitro assay conditions, in which a key regulatory molecule or protein was absent.
biosynthesis, virulence, gene cluster, capsule, Escherichia coli K1
Structure type: homopolymer
Location inside paper: p.706
Trivial name: colominic acid sodium salt, colominic acid, type B polysaccharide, polysialic acid, PSA, oligosaccharide repeating unit, α-2,8-linked polysialic acid
Compound class: CPS, O-polysaccharide, K-antigen, O-antigen
Contained glycoepitopes: IEDB_136794,IEDB_141115,IEDB_142352,IEDB_146100,IEDB_149174,IEDB_150072,IEDB_150937,IEDB_153199,IEDB_226810,IEDB_558870,IEDB_983929,SB_170,SB_171,SB_172,SB_35,SB_42,SB_84
Biosynthesis and genetic data: genetic data
NCBI Taxonomy refs (TaxIDs): 1392869Reference(s) to other database(s): GTC:G30588ZL, GlycomeDB:
677
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There is only one chemically distinct structure:
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