MitoNEET is the only identified Fe-S protein localized to the outer mitochondrial membrane and a 1.5 A resolution X-ray analysis has revealed a unique structure [Paddock et al. (2007), Proc. Natl Acad. Sci. USA, 104, 14342-14347]. The 2Fe-2S cluster is bound with a 3Cys-1His coordination which defines a new class of 2Fe-2S proteins. The hallmark feature of this class is the single noncysteine ligand His87, which when replaced by Cys decreases the redox potential (E(m)) by approximately 300 mV and increases the stability of the cluster by around sixfold. Unexpectedly, the pH dependence of the lifetime of the 2Fe-2S cluster remains the same as in the wild-type protein. Here, the crystal structure of H87C mitoNEET was determined to 1.7 A resolution (R factor = 18%) to investigate the structural basis of the changes in the properties of the 2Fe-2S cluster. In comparison to the wild type, structural changes are localized to the immediate vicinity of the cluster-binding region. Despite the increased stability, Cys87 displays two distinct conformations, with distances of 2.3 and 3.2 A between the S(gamma) and the outer Fe of the 2Fe-2S cluster. In addition, Lys55 exhibits multiple conformations in the H87C mutant protein. The structure and distinct characteristics of the H87C mutant provide a framework for further studies investigating the effects of mutation on the properties of the 2Fe-2S cluster in this new class of proteins.
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机译：MitoNEET是唯一标识Fe-S蛋白质外线粒体膜和本地化1.5解决x射线分析揭示了独特的结构[Paddock Proc et al .(2007)。《科学。2 3 cys-1his fe-2s集群必然协调2 fe-2s的定义一个新类蛋白质。当单一noncysteine配体His87取而代之的是半胱氨酸氧化还原电位降低(E (m))约300 mV和增加了集群的稳定性6倍左右。出乎意料,pH值依赖的一生2 fe-2s集群仍然是一样的野生型蛋白。1.7 H87C mitoNEET决心解决(R因子= 18%)对结构进行调查的属性变化的基础2 fe-2s集群。结构调整是最直接的本地化cluster-binding附近地区。增加稳定性,Cys87显示两个不同的构象,距离为2.33.2之间的年代(γ)和外铁2 fe-2s集群。多重构象H87C突变蛋白质。H87C突变体提供的特性进一步的研究调查的框架突变的性质的影响2 fe-2s集群在这个新类的蛋白质。
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