The sialyl-T antigen, sialylα2-3Galβ1-3GalNAc-, is a common O-glycan structure in human glycoproteins and is synthesized by sialyltransferase ST3Gal1. The enterohemorrhagic Escherichia coli serotype O104 has the rare ability to synthesize a sialyl-T antigen mimic. We showed here that the wbwA gene of the E. coli O104 antigen synthesis gene cluster encodes an α2,3-sialyltransferase WbwA that transfers sialic acid from CMP-sialic acid to Galβ1-3GalNAc-α-diphosphate-lipid acceptor. The NMR analysis of purified WbwA enzyme reaction product indicated that the sialyl-T antigen, sialylα2-3Galβ1-3GalNAc-α-diphosphate-lipid, was synthesized. We showed that the conserved HP motif, and Glu/Asp residues of two EDG motifs in WbwA are important for the activity. The characterization studies showed that WbwA from E. coli O104 is a monofunctional α2,3-sialyltransferase, and is distinct from human ST3Gal1 as well as all other known sialyltransferases due to its unique acceptor specificity. This work contributes to knowledge of the biosynthesis of bacterial virulence factors. IMPORTANCE: This is the first characterization of a sialyltransferase involved in the synthesis of an O antigen in E. coli. The enzyme contributes to the mimicry of human sialyl-T antigen and has a unique substrate specificity but very little sequence identity with other sialyltransferases. Thus the bacterial sialyltransferase is related to the human counterpart only by the similarity of biochemical activity.
O-antigen, sialyltransferase, Substrate Specificity, O antigen synthesis, E.coli O104, Enterohemorrhagic Escherichia coli, sialyl-T antigen, ST3Gal1, WbwA
NCBI PubMed ID: 26391208Publication DOI: 10.1128/JB.00521-15Journal NLM ID: 2985120RPublisher: American Society for Microbiology
Correspondence: brockhau@queensu.ca
Institutions: Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, USA, TumorEnd, Baton Rouge, Louisiana, USA, Department of Chemistry, Queen's University, Kingston, Ontario, Canada, Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, K7L3N6 Canada
Methods: 13C NMR, 1H NMR, NMR-2D, SDS-PAGE, glycosyltransferase assays, ESI-MS, Western blotting, NMR-1D, genetic methods, biochemical methods, radioactivity measurement, HPLC
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