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Electrochemical experiments define the potentials associated with binding of substrates and inhibitors to nitrogenase MoFe protein

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posted on 2023-05-03, 15:02 authored by Ting Chen, Philip A Ash, Lance Seefeldt, Kylie A Vincent

Nitrogenases catalyse the 6-electron reduction of dinitrogen to ammonia, passing through a series of redox and protonation levels during catalytic substrate reduction. The molybdenum–iron nitrogenase is the most well-studied, but redox potentials associated with proton-coupled transformations between the redox levels of the catalytic MoFe protein have proved difficult to pin down, in part due to a complex electron-transfer pathway from the partner Fe protein, linked to ATP-hydrolysis. Here, we apply electrochemical control to the MoFe protein of Azotobacter vinelandii nitrogenase, using europium(III/II)-ligand couples as low potential redox mediators. We combine insight from the electrochemical current response with data from gas chromatography and in situ infrared spectroscopy, in order to define potentials for the binding of a series of inhibitors (carbon monoxide, methyl isocyanide) to the metallo-catalytic site of the MoFe protein, and the onset of catalytic transformation of alternative substrates (protons and acetylene) by the enzyme. Thus, we associate potentials with the redox levels for inhibition and catalysis by nitrogenase, with relevance to the elusive mechanism of biological nitrogen fixation.

History

Author affiliation

Department of Chemistry, University of Leicester

Version

  • VoR (Version of Record)

Published in

Faraday Discussions

Publisher

Royal Society of Chemistry (RSC)

issn

1359-6640

eissn

1364-5498

Acceptance date

2023-02-06

Copyright date

2023

Available date

2023-05-03

Language

en

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