Bönisch Heiko, Schmidt Christian L, Schäfer Günter, Ladenstein Rudolf
Department of Biosciences at NOVUM, Center for Structural Biochemistry, Karolinska Institutet, Hälsovägen 7-9, S-14157 Huddinge, Sweden.
J Mol Biol. 2002 Jun 7;319(3):791-805. doi: 10.1016/S0022-2836(02)00323-6.
The first crystal structure of an archaeal Rieske iron-sulfur protein, the soluble domain of Rieske iron-sulfur protein II (soxF) from the hyperthermo-acidophile Sulfolobus acidocaldarius, has been solved by multiple wavelength anomalous dispersion (MAD) and has been refined to 1.1 A resolution. SoxF is a subunit of the terminal oxidase supercomplex SoxM in the plasma membrane of S. acidocaldarius that combines features of a cytochrome bc(1) complex and a cytochrome c oxidase. The [2Fe-2S] cluster of soxF is most likely the primary electron acceptor during the oxidation of caldariella quinone by the cytochrome a(587)/Rieske subcomplex. The geometry of the [2Fe-2S] cluster and the structure of the cluster-binding site are almost identical in soxF and the Rieske proteins from eucaryal cytochrome bc(1) and b(6)f complexes, suggesting a strict conservation of the catalytic mechanism. The main domain of soxF and part of the cluster-binding domain, though structurally related, show a significantly divergent structure with respect to topology, non-covalent interactions and surface charges. The divergent structure of soxF reflects a different topology of the soxM complex compared to eucaryal bc complexes and the adaptation of the protein to the extreme ambient conditions on the outer membrane surface of a hyperthermo-acidophilic organism.
嗜热嗜酸菌嗜酸热硫化叶菌（Sulfolobus acidocaldarius）的 Rieske 铁硫蛋白 II（soxF）的可溶性结构域——一种古生菌 Rieske 铁硫蛋白的首个晶体结构，已通过多波长反常散射（MAD）解析，并精修至 1.1 Å 分辨率。SoxF 是嗜酸热硫化叶菌质膜中末端氧化酶超复合物 SoxM 的一个亚基，它兼具细胞色素 bc(1) 复合物和细胞色素 c 氧化酶的特征。SoxF 的 [2Fe-2S] 簇很可能是细胞色素 a(587)/Rieske 亚复合物氧化卡尔达里醌过程中的主要电子受体。SoxF 中 [2Fe-2S] 簇的几何结构以及簇结合位点的结构，与真核生物细胞色素 bc(1) 和 b(6)f 复合物中的 Rieske 蛋白几乎相同，这表明催化机制具有严格的保守性。SoxF 的主要结构域和部分簇结合结构域虽然在结构上相关，但在拓扑结构、非共价相互作用和表面电荷方面显示出显著不同的结构。SoxF 的不同结构反映出与真核生物 bc 复合物相比，SoxM 复合物具有不同的拓扑结构，以及该蛋白对嗜热嗜酸生物外膜表面极端环境条件的适应性。
