Structural Views Along the Mycobacterium Tuberculosis MenD Reaction Pathway Illuminate Key Aspects of Thiamin Diphosphate-Dependent Enzyme Mechanisms

Structure. 2016 Jul 6;24(7):1167-77. doi: 10.1016/j.str.2016.04.018. Epub 2016 Jun 9.

Abstract

Menaquinone (MQ) is an essential component of the respiratory chains of many pathogenic organisms, including Mycobacterium tuberculosis (Mtb). The first committed step in MQ biosynthesis is catalyzed by 2-succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexadiene-1-carboxylate synthase (MenD), a thiamin diphosphate (ThDP)-dependent enzyme. Catalysis proceeds through two covalent intermediates as the substrates 2-oxoglutarate and isochorismate are successively added to the cofactor before final cleavage of the product. We have determined a series of crystal structures of Mtb-MenD that map the binding of both substrates, visualizing each step in the MenD catalytic cycle, including both intermediates. ThDP binding induces a marked asymmetry between the coupled active sites of each dimer, and possible mechanisms of communication can be identified. The crystal structures also reveal conformational features of the two intermediates that facilitate reaction but prevent premature product release. These data fully map chemical space to inform early-stage drug discovery targeting MenD.

Keywords: MenD; crystal structures; menaquinone biosynthesis; reaction intermediates; thiamin diphosphate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Catalytic Domain
  • Molecular Dynamics Simulation
  • Mycobacterium tuberculosis / enzymology*
  • Protein Binding
  • Protein Multimerization
  • Pyruvate Oxidase / chemistry*
  • Pyruvate Oxidase / metabolism
  • Thiamine / metabolism

Substances

  • Bacterial Proteins
  • Pyruvate Oxidase
  • Thiamine