Hunsicker-Wang Laura M, Heine Andreas, Chen Ying, Luna Eugene P, Todaro Thomas, Zhang Yan Ming, Williams Pamela A, McRee Duncan E, Hirst Judy, Stout C David, Fee James A
Division of Biology, the University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
Biochemistry. 2003 Jun 24;42(24):7303-17. doi: 10.1021/bi0342719.
The structure of the soluble Rieske protein from Thermus thermophilus has been determined at a resolution of 1.3 A at pH 8.5 using multiwavelength anomalous dispersion (MAD) techniques. This is the first report of a Rieske protein from a menaquinone-utilizing organism. The structure shows an overall fold similar to previously reported Rieske proteins. A novel feature of this crystal form appears to be a shared hydrogen between the His-134 imidazole ring ligated to Fe2 of the [2Fe-2S] cluster and its symmetry partner, His-134', one being formally an imidazolate anion, Fe2-(His-134)N(epsilon)(-)...H-N(epsilon')(His-134')-Fe2', in which crystallographic C(2) axes pass equidistant between N(epsilon)...N(epsilon') and normal to the line defined by N(epsilon)...N(epsilon'). This provides evidence for a stable, oxidized cluster with a His(-) ligand and lends support to a previously proposed mechanism of coupled proton and electron transfer. A detailed comparison of the Thermus Rieske protein with six other Rieske and Rieske-type proteins indicates: (a) The cluster binding domain is tightly conserved. (b) The 3-D structure of the 10 beta-strand fold is conserved, even among the most divergent proteins. (c) There is an approximately linear relation between acid-pH redox potential and number of H-bonds to the cluster. (d) These proteins have two faces, one points into the larger complex (bc(1), b(6)f, or other), is involved in the proton coupled electron transfer function, and is highly conserved. The second is oriented toward the solvent and shows wide variation in charge, sequence, length, hydrophobicity, and secondary elements in the loops that connect the beta-sheets.
嗜热栖热菌可溶性 Rieske 蛋白的结构已通过多波长反常色散（MAD）技术在 pH 8.5 条件下以 1.3 Å 的分辨率测定。这是关于来自利用甲萘醌的生物体的 Rieske 蛋白的首次报道。该结构显示出与先前报道的 Rieske 蛋白总体折叠相似。这种晶体形式的一个新特征似乎是连接到 [2Fe-2S] 簇的 Fe2 的 His-134 咪唑环与其对称伙伴 His-134' 之间共享一个氢，其中一个形式上是咪唑阴离子，Fe2-(His-134)N(ε)(-)...H-N(ε')(His-134')-Fe2'，其中晶体学 C2 轴在 N(ε)...N(ε') 之间等距穿过且垂直于由 N(ε)...N(ε') 定义的线。这为具有 His(-) 配体的稳定氧化簇提供了证据，并支持了先前提出的质子和电子耦合转移机制。嗜热栖热菌 Rieske 蛋白与其他六种 Rieske 和 Rieske 型蛋白的详细比较表明：（a）簇结合结构域高度保守。（b）即使在差异最大的蛋白质中，10 条β链折叠的三维结构也保守。（c）酸 - pH 氧化还原电位与簇的氢键数量之间存在近似线性关系。（d）这些蛋白质有两个面，一个指向更大的复合物（bc(1)、b(6)f 或其他），参与质子耦合电子转移功能，并且高度保守。第二个面朝向溶剂，在连接β片层的环中的电荷、序列、长度、疏水性和二级结构元件方面显示出广泛变化。
