Crystal structure of a UDP-GlcNAc epimerase for surface polysaccharide biosynthesis in Acinetobacter baumannii

Bhumika S. Shah, Heather E. Ashwood, Stephen J. Harrop, Daniel N. Farrugia, Ian T. Paulsen, Bridget C. Mabbutt*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    1 Citation (Scopus)
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    Abstract

    With new strains of Acinetobacter baumannii undergoing genomic analysis, it has been possible to define regions of genomic plasticity (RGPs), encoding specific adaptive elements. For a selected RGP from a community-derived isolate of A. baumannii, we outline sequences compatible with biosynthetic machinery of surface polysaccharides, specifically enzymes utilized in the dehydration and conversion of UDP-N-acetyl-D-glucosamine (UDP-D-GlcNAc). We have determined the crystal structure of one of these, the epimerase Ab-WbjB. This dehydratase belongs to the 'extended' short-chain dehydrogenase/reductase (SDR) family, related in fold to previously characterised enzymes CapE and FlaA1. Our 2.65Å resolution structure of Ab-WbjB shows a hexamer, organised into a trimer of chain pairs, with coenzyme NADP+ occupying each chain. Specific active-site interactions between each coenzyme and a lysine quaternary group of a neighbouring chain interconnect adjacent dimers, so stabilising the hexameric form. We show UDP-GlcNAc to be a specific substrate for Ab-WbjB, with binding evident by ITC (Ka = 0.23 μmol-1). The sequence of Ab-WbjB shows variation from the consensus active-site motifs of many SDR enzymes, demonstrating a likely catalytic role for a specific threonine sidechain (as an alternative to tyrosine) in the canonical active site chemistry of these epimerases.

    Original languageEnglish
    Article numbere0191610
    Pages (from-to)1-19
    Number of pages19
    JournalPLoS ONE
    Volume13
    Issue number1
    DOIs
    Publication statusPublished - 19 Jan 2018

    Bibliographical note

    Copyright the Author(s) 2018. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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