Dambe Tresfore, Quentmeier Armin, Rother Dagmar, Friedrich Cornelius, Scheidig Axel J
Max-Planck-Institut für Molekulare Physiologie, Abteilung Physikalische Biochemie, Otto-Hahn-Strasse 11, D-44225 Dortmund, Germany.
J Struct Biol. 2005 Dec;152(3):229-34. doi: 10.1016/j.jsb.2005.09.002. Epub 2005 Nov 2.
The sulfur-oxidizing enzyme system (Sox) of the chemotroph Paracoccus pantotrophus is composed of several proteins, which together oxidize hydrogen sulfide, sulfur, thiosulfate or sulfite and transfers the gained electrons to the respiratory chain. The hetero-dimeric cytochrome c complex SoxXA functions as heme enzyme and links covalently the sulfur substrate to the thiol of the cysteine-138 residue of the SoxY protein of the SoxYZ complex. Here, we report the crystal structure of the c-type cytochrome complex SoxXA. The structure could be solved by molecular replacement and refined to a resolution of 1.9A identifying the axial heme-iron coordination involving an unusual Cys-251 thiolate of heme2. Distance measurements between the three heme groups provide deeper insight into the electron transport inside SoxXA and merge in a better understanding of the initial step of the aerobic sulfur oxidation process in chemotrophic bacteria.
化能营养型泛养副球菌的硫氧化酶系统（Sox）由几种蛋白质组成，这些蛋白质共同氧化硫化氢、硫、硫代硫酸盐或亚硫酸盐，并将获得的电子传递到呼吸链。异源二聚体细胞色素c复合物SoxXA作为血红素酶发挥作用，并将硫底物与SoxYZ复合物中SoxY蛋白半胱氨酸-138残基的硫醇共价连接。在此，我们报道了c型细胞色素复合物SoxXA的晶体结构。该结构可以通过分子置换法解析，并精修至1.9埃的分辨率，确定了涉及血红素2中一个不寻常的半胱氨酸-251硫醇盐的轴向血红素-铁配位。三个血红素基团之间的距离测量为深入了解SoxXA内部的电子传递提供了更多信息，并有助于更好地理解化能营养型细菌中需氧硫氧化过程的初始步骤。
