Influence of the environment on the [4Fe−4S]2+ to [2Fe−2S]2+ cluster switch in the transcriptional regulator FNR

Crack, Jason C., Gaskell, Alisa A., Green, Jeffrey, Cheesman, Myles R., Le Brun, Nick E. ORCID: https://orcid.org/0000-0001-9780-4061 and Thomson, Andrew J. (2008) Influence of the environment on the [4Fe−4S]2+ to [2Fe−2S]2+ cluster switch in the transcriptional regulator FNR. Journal of the American Chemical Society, 130 (5). pp. 1749-1758.

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Abstract

In Escherichia coli, the switch between aerobic and anaerobic metabolism is primarily controlled by the fumarate and nitrate reduction transcriptional regulator FNR. In the absence of O2, FNR binds a [4Fe-4S]2+ cluster, generating a transcriptionally active dimeric form. Exposure to O2 results in the conversion of the cluster to a [2Fe-2S]2+ form, leading to dissociation of the protein into transcriptionally inactive monomers. The [4Fe-4S]2+ to [2Fe-2S]2+ cluster conversion proceeds in two steps. Step 1 involves the one-electron oxidation of the cluster, resulting in the release of Fe2+, generating a [3Fe-4S]1+ cluster intermediate, and a superoxide ion. In step 2, the cluster intermediate spontaneously rearranges to form the [2Fe-2S]2+ cluster, with the release of a Fe3+ ion and two sulfide ions. Here, we demonstrate that, in both native and reconstituted [4Fe-4S] FNR, the reaction environment and, in particular, the presence of Fe2+ and/or Fe3+ chelators can influence significantly the cluster conversion reaction. We demonstrate that while the rate of step 1 is largely insensitive to chelators, that of step 2 is significantly enhanced by both Fe2+ and Fe3+ chelators. We show that, for reactions in Fe3+-coordinating phosphate buffer, step 2 is enhanced to the extent that step 1 becomes the rate determining step and the [3Fe-4S]1+ intermediate is no longer detectable. Furthermore, Fe3+ released during this step is susceptible to reduction in the presence of Fe2+ chelators. This work, which may have significance for the in vivo FNR cluster conversion reaction in the cell cytoplasm, provides an explanation for apparently contradictory results reported from different laboratories.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Chemistry of Light and Energy
Faculty of Science > Research Groups > Chemistry of Life Processes
Faculty of Science > Research Groups > Biophysical Chemistry (former - to 2017)
Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Depositing User: Rachel Smith
Date Deposited: 29 Mar 2011 12:27
Last Modified: 16 Jan 2023 17:31
URI: https://ueaeprints.uea.ac.uk/id/eprint/27419
DOI: 10.1021/ja077455+

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