Superoxide-mediated amplification of the oxygen-induced switch from [4Fe-4S] to [2Fe-2S] clusters in the transcriptional regulator FNR
Superoxide-mediated amplification of the oxygen-induced switch from [4Fe-4S] to [2Fe-2S] clusters in the transcriptional regulator FNR
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DOI：
10.1073/pnas.0609514104
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发表时间：
2007-02-13
影响因子：
11.1
通讯作者：
Thomson, Andrew J.
中科院分区：
文献类型：
--
作者：
Crack, Jason C.;Green, Jeffrey;Thomson, Andrew J.
在大肠杆菌中，需氧代谢和厌氧代谢之间的转换主要由FNR（富马酸盐和硝酸盐还原调节剂）控制，FNR是一种调节超过100个基因响应氧的转录的蛋白质。在氧限制条件下，FNR结合[4Fe-4S]（2+）簇，产生转录活性二聚体形式。在暴露于氧气时，簇转化为[2Fe-2S]（2+）形式，导致蛋白质解离成单体，其不能以高亲和力结合DNA。集群转换的机制与转换产物的性质是相当大的当前利益。在这里，我们证明了[4Fe-4S]2+到[2Fe-2S]2+的簇转化，在天然和重构的[4Fe-4S] FNR中，通过簇的单电子氧化进行，得到[3Fe-4S]（1+）簇中间体，并释放一个Fe 2+离子和一个超氧离子。簇中间体随后自发重排形成[2Fe-2S]2+簇，释放出一个Fe 3+离子和两个硫化物离子。超氧离子发生歧化成过氧化氢和氧气。这种机制，一个电子激活的集群，耦合到催化循环产生的超氧离子回到氧气，提供了一种手段，放大灵敏度的[4Fe-4S] FNR的信号分子。
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.