Taxonomic group: bacteria / Proteobacteria
(Phylum: Proteobacteria)
Associated disease: infection due to Escherichia coli [ICD11:
XN6P4 
]
NCBI PubMed ID: 9922239Journal NLM ID: 2985120RPublisher: American Society for Microbiology
Correspondence: cwhitfie
uoguelph.ca
Institutions: Department of Microbiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada, Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
Escherichia coli O8:K40 coexpresses two distinct lipopolysaccharide (LPS) structures on its surface. The O8 polysaccharide is a mannose homopolymer with a trisaccharide repeat unit and is synthesized by an ABC-2 transport-dependent pathway. The K40LPS backbone structure is composed of a trisaccharide repeating unit of N-acetylglucosamine (GlcNAc) and glucuronic acid (GlcA) and has an uncommon substitution, an L-serine moiety attached to glucuronic acid. The gene cluster responsible for synthesis of the K40 polysaccharide has previously been cloned and sequenced and was found to contain six open reading frames (ORFs) (P. A. Amor and C. Whitfield, Mol. Microbiol. 26:145-161, 1997). Here, we demonstrate that insertional inactivation of orf1 results in the accumulation of a semirough (SR)-K40LPS form which retains reactivity with specific polyclonal serum in Western immunoblots. Structural and compositional analysis of the SR-K40LPS reveals that it comprises a single K40 repeat unit attached to lipid A core. The lack of polymerization of the K40 polysaccharide indicates that orf1 encodes the K40 polymerase (Wzy) and that assembly of the K40 polysaccharide occurs via a Wzy-dependent pathway (in contrast to that of the O8 polysaccharide). Inactivation of orf3 also results in the accumulation of an SR-LPS form which fails to react with specific polyclonal K40 serum in Western immunoblots. Methylation linkage analysis and fast atom bombardment-mass spectrometry of this SR-LPS reveals that the biological repeat unit of the K40 polysaccharide is GlcNAc-GlcA-GlcNAc. Additionally, this structure lacks the L-serine substitution of GlcA. These results show that (i) orf3 encodes the enzyme responsible for the addition of the L-serine residue to the K40 backbone and (ii) substitution of individual K40 repeats with L-serine is essential for their recognition and polymerization into the K40 polysaccharide by Wzy.
biosynthesis, antigen, Escherichia, Escherichia coli, glycan, requirement, assembly, identification, backbone, enzyme, polymerization, L-serine
Structure type: polymer chemical repeating unit
Location inside paper: Fig.1
Compound class: CPS, K-antigen
Contained glycoepitopes: IEDB_115136,IEDB_137340,IEDB_140630,IEDB_141807,IEDB_150900,IEDB_151531,IEDB_423153
Methods: genetic methods
Biosynthesis and genetic data: genetic data
Comments, role: published polymerization frame was shifted for conformity with other records.
NCBI Taxonomy refs (TaxIDs): 562Reference(s) to other database(s): GlycomeDB:
33287
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There is only one chemically distinct structure:
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