Substrate recognition by a carbohydrate-binding module in the prototypical ABC transporter for lipopolysaccharide O-antigen from Escherichia coli O9a.

ABSTRACT: Escherichia coli serotype O9a provides a model for export of lipopolysaccharide (LPS) O-antigen polysaccharide (O-PS) via ABC transporters. In O9a biosynthesis, a chain-terminator enzyme, WbdD, caps the nonreducing end of the glycan with a methylphosphate moiety and thereby establishes chain-length distribution. A carbohydrate-binding module (CBM) in the ABC transporter recognizes terminated glycans, ensuring that only mature O-PS is exported and incorporated into LPS. Here, we addressed two questions arising from this model. Are both residues in the binary terminator necessary for termination and export? And is a terminal methylphosphate moiety sufficient for export of heterologous glycans? To answer the first question, we uncoupled WbdD kinase and methyltransferase activities. Wbd

SUBMITTER: Mann E 

PROVIDER: S-EPMC6791312 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature