Lipopolysaccharide O-antigen is an attractive candidate for immunotherapeutic strategies targeting antibiotic-resistant Klebsiella pneumoniae. Several K. pneumoniae O-serotypes are based on a shared O2a-antigen backbone repeating unit: (→3)-α-Galp-(1→3)-β-Galf-(1→). O2a antigen is synthesized on undecaprenol diphosphate in a pathway involving the O2a polymerase, WbbM, before its export by an ATP-binding cassette transporter. This dual domain polymerase possesses a C-terminal galactopyranosyltransferase resembling known GT8 family enzymes, and an N-terminal DUF4422 domain identified here as a galactofuranosyltransferase defining a previously unrecognized family (GT111). Functional assignment of DUF4422 explains how galactofuranose is incorporated into various polysaccharides of importance in vaccine production and the food industry. In the 2.1-Å resolution structure, three WbbM protomers associate to form a flattened triangular prism connected to a central stalk that orients the active sites toward the membrane. The biochemical, structural and topological properties of WbbM offer broader insight into the mechanisms of assembly of bacterial cell-surface glycans.
Lipopolysaccharide, O-antigen, mechanism, galactofuranose, glycosyltransferase, Klebsiella pneumoniae, O-antigen polymerase, vaccine, transporter, glycans, O-serotypes, undecaprenol
NCBI PubMed ID: 32152541Publication DOI: 10.1038/s41589-020-0494-0Journal NLM ID: 101231976Publisher: New York, NY: Nature Publishing Group
Correspondence: mkimber@uoguelph.ca; cwhitfie@uoguelph.ca
Institutions: Department of Chemistry, University of Alberta, Edmonton, AB, Canada, Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
Methods: 13C NMR, 1H NMR, gel filtration, NMR-2D, PCR, SDS-PAGE, DNA techniques, ESI-MS, biochemical methods, bioinformatic analysis, enzyme structure, topological information
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