Interactions between the cytochrome b, cytochrome c1, and Fe-S protein subunits at the ubihydroquinone oxidation site of the bc1 complex of Rhodobacter capsulatus.
Interactions between the cytochrome b, cytochrome c1, and Fe-S protein subunits at the ubihydroquinone oxidation site of the bc1 complex of Rhodobacter capsulatus.
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荚膜红杆菌 bc1 复合体的泛氢醌氧化位点上细胞色素 b、细胞色素 c1 和 Fe-S 蛋白亚基之间的相互作用。
DOI：
10.1021/bi973146s
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Daldal,F
中科院分区：
文献类型：
--
作者：
Saribas,AS;Valkova-Valchanova,M;Tokito,MK;Zhang,Z;Berry,EA;Daldal,F
泛氢醌：细胞色素（cyt）氧化还原酶（bc1复合物和其植物对应物b6f复合物）是从细菌到真核生物的大多数生物能量转换系统的重要组成部分。在兼性光养细菌Rhodococcus capsulatus中，它由cytb、cytc1和Rieske Fe − S蛋白亚基组成，对Ps的生长至关重要。在这些亚基中，cytb有两个非跨膜螺旋cd1和cd2，这两个螺旋对其结构和功能至关重要。特别是，用苯丙氨酸（F）或脯氨酸（P）取代cd1上163位的苏氨酸（T）导致bc1复合物的缺失。在这里，Ps+回复突变体的B：T163 F，其详细的表征表明，位置163是重要的组装的bc1复合物介导的亚基相互作用在Qosite。cytb的163位羟基的损失通过Fe-S蛋白cytbor 46的182位羟基或cytc1的46位巯基的增加来补偿。α-albc1复合物晶体结构的检验[Zhang，Z.，黄湖，加-地Shulmeister，V. M.，Chi，Y. -一、金，K. K.，洪湖W.，Crofts，A. R.，贝里，E.一、和Kim，S. - H.（1998）Nature 392，677 - 684]揭示了B：G182的对应物（即，G167）和F：A46（即，A70）位于靠近B：T163（即，T148），而C：R46（即，回复突变体含有亚化学计量的Fe-S蛋白亚基，并表现出稳态和单次转换，电子转移活性低于野生型bc1复合物。有趣的是，它们的膜上清液含有这种亚基的较小形式，其理化性质与其膜结合形式相同。对这种可溶性Fe − S蛋白的氨基末端氨基酸序列的测定表明，它是通过V44的蛋白水解裂解从野生型蛋白衍生而来的。这项工作首次揭示了cytbis的163位对于Qosite上的适当亚基相互作用和bc1复合物的失活都很重要，bc1复合物的失活是通过在Qosite催化过程中明显负责其流动性的区域对其Fe − S蛋白亚基进行蛋白水解裂解来实现的。
Ubihydroquinone:cytochrome (cyt)coxidoreductase (bc1complex and its plant counterpartb6fcomplex) is a vital component of energy-transducing systems in most organisms from bacteria to eukaryotes. In the facultative phototrophic (Ps) bacteriumRhodobactercapsulatus, it is constituted by the cytb, cytc1, and Rieske Fe−S protein subunits and is essential for Ps growth. Of these subunits, cytbhas two nontransmembrane helices,cd1 andcd2, which are critical for its structure and function. In particular, substitution of threonine (T) at position 163 oncd1 with phenylalanine (F) or proline (P) leads to the absence of thebc1complex. Here, Ps+revertants of B:T163F were obtained, and their detailed characterizations indicated that position 163 is important for the assembly of thebc1complex by mediating subunit interactions at the Qosite. The loss of the hydroxyl group at position 163 of cytbwas compensated for by the gain of either a hydroxyl group at position 182 of cytbor 46 of the Fe−S protein or a sulfhydryl group at position 46 of cytc1. Examination of the mitochondrialbc1complex crystal structure [Zhang, Z., Huang, L., Shulmeister, V. M., Chi, Y.-I., Kim, K. K., Hung, L.-W., Crofts, A. R., Berry, E. A., and Kim, S.-H. (1998)Nature 392, 677−684] revealed that the counterparts of B:G182 (i.e., G167) and F:A46 (i.e., A70) are located close to B:T163 (i.e., T148), whereas the C:R46 (i.e., R28) is remarkably far from it. The revertants contained substoichiometric amounts of the Fe−S protein subunit and exhibited steady-state and single-turnover, electron transfer activities lower than that of a wild-typebc1complex. Interestingly, their membrane supernatants contained a smaller form of this subunit with physicochemical properties identical to those of its membrane-bound form. Determination of the amino-terminal amino acid sequence of this soluble Fe−S protein revealed that it was derived from the wild-type protein by proteolytic cleavage at V44. This work revealed for the first time that position 163 of cytbis important both for proper subunit interactions at the Qosite and for inactivation of thebc1complex by proteolytic cleavage of its Fe−S protein subunit at a region apparently responsible for its mobility during Qosite catalysis.