Identification and Biochemical Characterization of the Novel ?2,3-Sialyltransferase WbwA from Pathogenic Escherichia coli Serotype O104.
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ABSTRACT: The sialyl-T antigen sialyl?2-3Gal?1-3GalNAc 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 ?2,3-sialyltransferase WbwA that transfers sialic acid from CMP-sialic acid to Gal?1-3GalNAc?-diphosphate-lipid acceptor. Nuclear magnetic resonance (NMR) analysis of purified WbwA enzyme reaction product indicated that the sialyl-T antigen sialyl?2-3Gal?1-3GalNAc?-diphosphate-lipid was synthesized. We showed that the conserved His-Pro (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 ?2,3-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.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 unique substrate specificity but very little sequence identity to other sialyltransferases. Thus, the bacterial sialyltransferase is related to the human counterpart only by the similarity of biochemical activity.
SUBMITTER: Czuchry D
PROVIDER: S-EPMC4652054 | biostudies-literature | 2015 Dec
REPOSITORIES: biostudies-literature
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