Redox and chemical activities of the hemes in the sulfur oxidation pathway enzyme SoxAX

Bradley, Justin M., Marritt, Sophie J., Kihlken, Margaret A., Haynes, Kate, Hemmings, Andrew M. ORCID: https://orcid.org/0000-0003-3053-3134, Berks, Ben C., Cheesman, Myles R. and Butt, Julea N. ORCID: https://orcid.org/0000-0002-9624-5226 (2012) Redox and chemical activities of the hemes in the sulfur oxidation pathway enzyme SoxAX. Journal of Biological Chemistry, 287 (48). pp. 40350-40359. ISSN 0021-9258

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Abstract

SoxAX enzymes couple disulfide bond formation to the reduction of cytochrome c in the first step of the phylogenetically widespread Sox microbial sulfur oxidation pathway. Rhodovulum sulfidophilum SoxAX contains three hemes. An electrochemical cell compatible with magnetic circular dichroism at near infrared wavelengths has been developed to resolve redox and chemical properties of the SoxAX hemes. In combination with potentiometric titrations monitored by electronic absorbance and EPR, this method defines midpoint potentials (Em) at pH 7.0 of approximately +210, −340, and −400 mV for the His/Met, His/Cys−, and active site His/CysS−-ligated heme, respectively. Exposing SoxAX to S2O42−, a substrate analog with Em ∼−450 mV, but not Eu(II) complexed with diethylene triamine pentaacetic acid (Em ∼−1140 mV), allows cyanide to displace the cysteine persulfide (CysS−) ligand to the active site heme. This provides the first evidence for the dissociation of CysS− that has been proposed as a key event in SoxAX catalysis.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Chemistry (former - to 2024)
UEA Research Groups:	Faculty of Science > Research Groups > Plant Sciences Faculty of Science > Research Groups > Molecular Microbiology Faculty of Science > Research Groups > Chemistry of Life Processes Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry Faculty of Science > Research Groups > Biophysical Chemistry (former - to 2017) Faculty of Science > Research Groups > Energy Materials Laboratory Faculty of Science > Research Groups > Chemistry of Light and Energy
Depositing User:	Users 2731 not found.
Date Deposited:	09 Jan 2013 12:20
Last Modified:	31 Oct 2024 00:32
URI:	https://ueaeprints.uea.ac.uk/id/eprint/40723
DOI:	10.1074/jbc.M112.396192

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