Issue 10, 2015

Protonation state of the Cu4S2 CuZ site in nitrous oxide reductase: redox dependence and insight into reactivity

Abstract

Spectroscopic and computational methods have been used to determine the protonation state of the edge sulfur ligand in the Cu4S2 CuZ form of the active site of nitrous oxide reductase (N2OR) in its 3CuICuII (1-hole) and 2CuI2CuII (2-hole) redox states. The EPR, absorption, and MCD spectra of 1-hole CuZ indicate that the unpaired spin in this site is evenly delocalized over CuI, CuII, and CuIV. 1-hole CuZ is shown to have a μ2-thiolate edge ligand from the observation of S–H bending modes in the resonance Raman spectrum at 450 and 492 cm−1 that have significant deuterium isotope shifts (−137 cm−1) and are not perturbed up to pH 10. 2-hole CuZ is characterized with absorption and resonance Raman spectroscopies as having two Cu–S stretching vibrations that profile differently. DFT models of the 1-hole and 2-hole CuZ sites are correlated to these spectroscopic features to determine that 2-hole CuZ has a μ2-sulfide edge ligand at neutral pH. The slow two electron (+1 proton) reduction of N2O by 1-hole CuZ is discussed and the possibility of a reaction between 2-hole CuZ and O2 is considered.

Graphical abstract: Protonation state of the Cu4S2 CuZ site in nitrous oxide reductase: redox dependence and insight into reactivity

Supplementary files

Article information

Article type
Edge Article
Submitted
10 Jun 2015
Accepted
03 Jul 2015
First published
03 Jul 2015
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2015,6, 5670-5679

Protonation state of the Cu4S2 CuZ site in nitrous oxide reductase: redox dependence and insight into reactivity

E. M. Johnston, S. Dell'Acqua, S. R. Pauleta, I. Moura and E. I. Solomon, Chem. Sci., 2015, 6, 5670 DOI: 10.1039/C5SC02102B

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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