Structure of cytochrome c′: a dimeric, high-spin haem protein
Structure of cytochrome c′: a dimeric, high-spin haem protein
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细胞色素 câ 的结构：二聚体、高自旋血红素蛋白
作者：
P. Weber;R. G. Bartsch;M. Cusanovich;R. Hamlin;Andrew Howard;S. Jordan;Martin D. Kamen;Terrance E. Meyer;D. Weatherford;N. Xuong;Francis Raymond Salemme
细菌细胞色素c′（参考文献1）存在于各种光合细菌和光合细菌中，它们被认为在电子传递中起作用2。大多数细胞色素c′分离为二聚体分子，由两个相同的分子量（MW）为14，000的亚基组成，每条多肽链包含一个原血红素IX辅基，通过两个半胱氨酸侧链与血红素乙烯基缩合形成的硫醚键共价结合3。虽然在研究充分的线粒体细胞色素c家族成员中发现了类似的共价血红素连接模式4，但细胞色素c′是相反的高自旋血红素蛋白（因此是主要名称），其结合中性配体5，通常与氧结合球蛋白家族成员相关的特征特性6。在这里，我们提出了一个初步的结构描述的细胞色素c′来自光合作用，紫色的非硫细菌Rhodocellum molischianum，并表明，它承担的结构相似性，无论是细胞色素c或珠蛋白结构家族的成员。相反，细胞色素c′单体结构主要组织为左扭曲的4-α-螺旋束，这是以前在其他几种顺序和功能无关的蛋白质中观察到的结构基序7 13。
The bacterial cytochromes c′ (ref. 1) occur in various photosynthetic and denitrifying bacteria, where they are presumed to function in electron transport2. Most cytochromes c′ are isolated as dimeric molecules composed of two identical subunits of ∼14,000 molecular weight (MW), with each polypeptide chain incorporating a protohaem IX prosthetic group covalently bound through thioether linkages formed by condensation of two cysteine side chains with the haem vinyl groups3. Although a similar mode of covalent haem attachment is found in members of the well studied mitochondrial cytochrome c family4, the cytochromes c′ are, in contrast, high-spin haem proteins (hence the prime designation) which bind neutral ligands5, characteristic properties generally associated with members of the oxygen-binding globin family6. Here we present a preliminary structural description of the cytochrome c′ derived from the photosynthetic, purple non-sulphur bacterium Rhodospirillum molischianum, and show that it bears little structural resemblance to members of either the cytochrome c or globin structural families. The cytochrome c′ monomer structure is, instead, principally organized as a left-twisted, 4-α-helical bundle, a structural motif previously observed in several other sequentially and functionally unrelated proteins7 13.