Structure and function of sedoheptulose-7-phosphate isomerase, a critical enzyme for lipopolysaccharide biosynthesis and a target for antibiotic adjuvants

Patricia L Taylor, Kim M Blakely, Gladys P de Leon, John R Walker, Fiona McArthur, Elena Evdokimova, Kun Zhang, Miguel A Valvano, Gerard D Wright, Murray S Junop

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

The barrier imposed by lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria presents a significant challenge in treatment of these organisms with otherwise effective hydrophobic antibiotics. The absence of L-glycero-D-manno-heptose in the LPS molecule is associated with a dramatically increased bacterial susceptibility to hydrophobic antibiotics and thus enzymes in the ADP-heptose biosynthesis pathway are of significant interest. GmhA catalyzes the isomerization of D-sedoheptulose 7-phosphate into D-glycero-D-manno-heptose 7-phosphate, the first committed step in the formation of ADP-heptose. Here we report structures of GmhA from Escherichia coli and Pseudomonas aeruginosa in apo, substrate, and product-bound forms, which together suggest that GmhA adopts two distinct conformations during isomerization through reorganization of quaternary structure. Biochemical characterization of GmhA mutants, combined with in vivo analysis of LPS biosynthesis and novobiocin susceptibility, identifies key catalytic residues. We postulate GmhA acts through an enediol-intermediate isomerase mechanism.
Original languageEnglish
Pages (from-to)2835-45
Number of pages11
JournalJournal of Biological Chemistry
Volume283
Issue number5
DOIs
Publication statusPublished - 01 Feb 2008

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

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