The primary structure of soluble cytochrome c-551 from the phototrophic green sulfur bacterium Chlorobium limicola, strain Tassajara, reveals a novel c-type cytochrome.
The primary structure of soluble cytochrome c-551 from the phototrophic green sulfur bacterium Chlorobium limicola, strain Tassajara, reveals a novel c-type cytochrome.
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来自光养绿硫细菌 Chlorobium limicola（Tassajara 菌株）的可溶性细胞色素 c-551 的一级结构揭示了一种新型 c 型细胞色素。
DOI：
10.1021/bi9806706
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
VanBeeumen,J
中科院分区：
文献类型：
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作者：
Klarskov,K;Verte,F;VanDriessche,G;Meyer,TE;Cusanovich,MA;VanBeeumen,J
胞色素-551是一种可溶性二聚体蛋白，含有相同的亚基，约30 kDa。氨基酸序列由自动Edman降解和质量分析相结合确定。258个残基中有一个单一的血红素结合位点位于半胱氨酸位置172和175。此外，在Cys78和Cys109之间有一个二硫桥，219位有一个游离半胱氨酸，以半胱酸的形式出现。可溶性细胞色素-551唯一的同源物是soxA蛋白，它是反硝化副球菌硫代硫酸盐利用操纵子的一部分。它们有32%相同，只有三个小缺口。这与细胞色素-551是硫代硫酸盐氧化酶的电子受体的观察结果是一致的。根据135 mV的氧化还原电位，第六血红素配体应该是蛋氨酸。在-551中存在的7个蛋氨酸残基中，只有一个是保守的，在血红素结合位点前面的两个残基。远紫外圆二色光谱显示40% α螺旋结构和25% β二级结构。没有其他已知的细胞色素机制具有这样的混合结构；它们要么都是螺旋形，要么都是β形。因此，氯溶性细胞色素-551和soxA可能是一类新的c型细胞色素的代表。
Chlorobium limicola,strain Tassajara, cytochromec-551 is a soluble dimeric protein containing identical subunits of about 30 kDa. The amino acid sequence was determined by a combination of automated Edman degradation and mass analysis. There are 258 residues with a single heme binding site located at cysteine positions 172 and 175. In addition, there is a disulfide bridge between Cys78 and Cys109, and a free cysteine at position 219 which was found to occur as cysteic acid. The only homologue of soluble cytochromec-551 is the soxA protein which is part of the thiosulfate utilization operon ofParacoccus denitrificans. They are 32% identical with three small gaps. This is consistent with the observation that cytochromec-551 is the electron acceptor for a thiosulfate-oxidizing enzyme. On the basis of the redox potential of 135 mV, the sixth heme ligand should be a methionine. Among the seven methionine residues that are present inc-551, only one is conserved, two residues ahead of the heme-binding site. The far-UV circular dichroism spectrum indicates 40% α helix and 25% β secondary structure. No other known cytochromechas such a mixed structure; they are either all helical or all β. Thus,Chlorobiumsoluble cytochromec-551 and soxA are likely to be representative of a new class ofc-type cytochromes.