Structural highlights
Publication Abstract from PubMedLipopolysaccharide 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)-alpha-Galp-(1 --> 3)-beta-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-A 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. A bifunctional O-antigen polymerase structure reveals a new glycosyltransferase family.,Clarke BR, Ovchinnikova OG, Sweeney RP, Kamski-Hennekam ER, Gitalis R, Mallette E, Kelly SD, Lowary TL, Kimber MS, Whitfield C Nat Chem Biol. 2020 Apr;16(4):450-457. doi: 10.1038/s41589-020-0494-0. Epub 2020 , Mar 9. PMID:32152541[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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