Opposites Attract: Escherichia coli heptosyltransferase i conformational changes induced by interactions between the substrate and positively charged residues

Joy M. Cote, Cody J.S. Hecht, Kaelan R. Patel, Carlos A. Ramirez-Mondragon, Yuk Y. Sham, Erika A. Taylor

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Gram-negative bacterial viability is greatly reduced by the disruption of heptose sugar addition during the biosynthesis of lipopolysaccharide (LPS), an important bacterial outer membrane component. Heptosyltransferase I (HepI), a member of the GT-B structural subclass of glycosyltransferases, is therefore an essential enzyme for the biosynthesis of the LPS. The disruption of HepI also increases the susceptibility of bacteria to hydrophobic antibiotics, making HepI a potential target for drug development. In this work, the structural and dynamic properties of the catalytic cycle of HepI are explored. Previously, substrate-induced stabilization of HepI was observed and hypothesized to be assisted by interactions between the substrate and residues located on dynamic loops. Herein, positively charged amino acids were probed to identify binding partners of the negatively charged phosphates and carboxylates of Kdo2-lipid A and its analogues. Mutant enzymes were characterized to explore changes in enzymatic activities and protein stability. Molecular modeling of HepI in the presence and absence of ligands was then performed with the wild type and mutant enzyme to allow determination of the relative change in substrate binding affinity resulting from each mutation. Together, these studies suggest that multiple residues are involved in mediating substrate binding, and a lack of additivity of these effects illustrates the functional redundancy of these binding interactions. The redundancy of residues mediating conformational transitions in HepI illustrates the evolutionary importance of these structural rearrangements for catalysis. This work enhances the understanding of HepI's protein dynamics and mechanism and is a model for improving our understanding of glycosyltransferase enzymes.

Original languageEnglish (US)
Pages (from-to)3135-3147
Number of pages13
JournalBiochemistry
Volume59
Issue number34
DOIs
StatePublished - Sep 1 2020

Bibliographical note

Funding Information:
E.A.T. and J.M.C. thank the National Institutes of Health for grant support (1R15AI119907-01). J.M.C. is grateful for support from a National Institutes of Health Doctoral Studies in Molecular Biophysics Training Grant (2T32GM008271-24).

Publisher Copyright:
Copyright © 2020 American Chemical Society.

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural

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