A conserved lysine residue controls iron-sulfur cluster redox chemistry in Escherichia coli fumarate reductase
A conserved lysine residue controls iron-sulfur cluster redox chemistry in Escherichia coli fumarate reductase
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DOI：
10.1016/j.bbabio.2013.05.004
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发表时间：
2013-10-01
影响因子：
4.3
通讯作者：
Weiner, Joel H.
中科院分区：
文献类型：
--
作者：
Cheng, Victor W. T.;Tran, Quang M.;Weiner, Joel H.
大肠杆菌呼吸复合物II旁系同源物琥珀酸脱氢酶（SdhCDAB）和富马酸还原酶（FrdABCD）分别催化与醌还原或氧化偶联的琥珀酸和富马酸的相互转化。基于两种酶的结构比较，在高度同源的可溶性结构域和发散的膜锚结构域之间的界面处的等效残基被靶向用于研究。这包括残基对SdhB-R205和FrdB-S203，以及保守的SdhB-K230和FrdB-K228对。这些残基的[3Fe-4S]簇和醌结合口袋的紧密接近提供了一个很好的机会，调查控制因素的[3Fe-4S]簇的还原电位，电子转移和催化的方向性，以及醌结合位点的结构和化学。我们的研究结果表明，SdhB-R205和SdhB-K230在微调[3Fe-4S]团簇和血红素的还原电位方面都起着重要的作用。在FrdABCD中，FrdB-S203的突变没有改变[3Fe-4S]簇的还原电位，但去除FrdB-K228处的碱性残基导致电位显著下移（>100 mV）。后一个残基对于醌结合和酶活性也是不可缺少的。对于FrdB-K228和Sdh-K230变体观察到的差异可归因于两种旁系同源物中醌结合位点的不同位置。虽然这个残基是绝对保守的，但它们在Frd和Sdh中已经分化以实现不同的功能。(C)2013爱思唯尔有限公司版权所有。
The Escherichia coli respiratory complex II paralogs succinate dehydrogenase (SdhCDAB) and fumarate reductase (FrdABCD) catalyze interconversion of succinate and fumarate coupled to quinone reduction or oxidation, respectively. Based on structural comparison of the two enzymes, equivalent residues at the interface between the highly homologous soluble domains and the divergent membrane anchor domains were targeted for study. This included the residue pair SdhB-R205 and FrdB-S203, as well as the conserved SdhB-K230 and FrdB-K228 pair. The close proximity of these residues to the [3Fe-4S] cluster and the quinone binding pocket provided an excellent opportunity to investigate factors controlling the reduction potential of the [3Fe-4S] cluster, the directionality of electron transfer and catalysis, and the architecture and chemistry of the quinone binding sites. Our results indicate that both SdhB-R205 and SdhB-K230 play important roles in fine tuning the reduction potential of both the [3Fe-4S] cluster and the heme. In FrdABCD, mutation of FrdB-S203 did not alter the reduction potential of the [3Fe-4S] cluster, but removal of the basic residue at FrdB-K228 caused a significant downward shift (>100 mV) in potential. The latter residue is also indispensable for quinone binding and enzyme activity. The differences observed for the FrdB-K228 and Sdh-K230 variants can be attributed to the different locations of the quinone binding site in the two paralogs. Although this residue is absolutely conserved, they have diverged to achieve different functions in Frd and Sdh. (C) 2013 Elsevier B.V. All rights reserved.