期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 104, 期 7, 页码 2092-2097出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0609514104
关键词
DNA regulation; iron-sulfur
资金
- Biotechnology and Biological Sciences Research Council [BB/C500836/1] Funding Source: Medline
- Wellcome Trust Funding Source: Medline
- Biotechnology and Biological Sciences Research Council [BB/C500836/1] Funding Source: researchfish
in Escherichia coli, the switch between aerobic and anaerobic metabolism is controlled primarily by FNR (regulator of fumarate and nitrate reduction), the protein that regulates the transcription of > 100 genes in response to oxygen. Under oxygen-limiting conditions, FNR binds a [4Fe-4S](2+) cluster, generating a transcriptionally active dimeric form. Upon exposure to oxygen the cluster converts to a [2Fe-2S](2+) form, leading to dissociation of the protein into monomers, which are incapable of binding DNA with high affinity. The mechanism of cluster conversion together with the nature of the products of conversion is of considerable current interest. Here, we demonstrate that [4Fe-4S]2+ to [2Fe-2S]2+ cluster conversion, in both native and reconstituted [4Fe-4S] FNR, proceeds via a one electron oxidation of the cluster, to give a [3Fe-4S](1+) cluster intermediate, with the release of one Fe2+ ion and a superoxide ion. The cluster intermediate subsequently rearranges spontaneously to form the [2Fe-2S]2+ cluster, with the release of a Fe3+ ion and, as previously shown, two sulfide ions. Superoxide ion undergoes dismutation to hydrogen peroxide and oxygen. This mechanism, a one electron activation of the cluster, coupled to catalytic recycling of the resulting superoxide ion back to oxygen, provides a means of amplifying the sensitivity of [4Fe-4S] FNR to its signal molecule.
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