Hydroxo-Bridged Active Site of Flavodiiron NO Reductase Revealed by Spectroscopy and Computations

09 September 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

NO and O2 are detoxified in many organisms using flavodiiron proteins (FDPs). The exact coordination of the iron centre in the active site of these enzymes remains unclear despite numerous structural studies. Here, we used 57Fe nuclear resonance vibrational spectroscopy (NRVS) to probe the iron-ligand interactions in Escherichia coli FDP. This data combined with density functional theory (DFT) and 57Fe Mössbauer spectroscopy indicate that the oxidised form of FDP contains a dihydroxo-diferric Fe(III)–(µOH)2–Fe(III) active site, while its reduction gives rise to a monohydroxo-diferrous Fe(II)–(µOH)–Fe(II) site upon elimination of one bridging OH ligand, thereby providing an open coordination site for NO binding. Prolonged NRVS data collection of the oxidised FDP resulted in photoreduction and formation of a partially reduced diiron center with two bridging hydroxyl ligands. These results have crucial implications for studying and understanding the mechanism of FDP as well as other non-haem diiron enzymes.

Keywords

FDP
NO reductase
NRVS
Mössbauer spectroscopy
DFT analyses
Catalytic Cycle Intermediates
Diiron Complex

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.