Electrochemical evidence that pyranopterin redox chemistry controls the catalysis of YedY, a mononuclear Mo enzyme

Hope Adamson, Alexandr Simonov, Michelina Kierzek, Richard Rothery, Joel Weiner, Alan Maxwell Bond, Alison Parkin

Research output: Contribution to journalArticleResearchpeer-review

27 Citations (Scopus)

Abstract

A long-standing contradiction in the field of mononuclear Mo enzyme research is that small-molecule chemistry on active-site mimic compounds predicts ligand participation in the electron transfer reactions, but biochemical measurements only suggest metal-centered catalytic electron transfer. With the simultaneous measurement of substrate turnover and reversible electron transfer that is provided by Fourier-transformed alternating-current voltammetry, we show that Escherichia coli YedY is a mononuclear Mo enzyme that reconciles this conflict. In YedY, addition of three protons and three electrons to the well-characterized "as-isolated" Mo(V) oxidation state is needed to initiate the catalytic reduction of either dimethyl sulfoxide or trimethylamine N-oxide. Based on comparison with earlier studies and our UV-vis redox titration data, we assign the reversible oneproton and one-electron reduction process centered around +174 mV vs. standard hydrogen electrode at pH 7 to a Mo(V)-to-Mo(IV) conversion but ascribe the two-proton and two-electron transition occurring at negative potential to the organic pyranopterin ligand system. We predict that a dihydro-to-tetrahydro transition is needed to generate the catalytically active state of the enzyme. This is a previously unidentified mechanism, suggested by the structural simplicity of YedY, a protein in which Mo is the only metal site.
Original languageEnglish
Pages (from-to)14506-14511
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume112
Issue number47
DOIs
Publication statusPublished - 2015

Keywords

  • Fourier-transformed alternating-current voltammetry
  • Mononuclear molybdenum enzyme
  • Protein film electrochemistry
  • Pyranopterin
  • YedY

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