The 1.5-A crystal structure of plastocyanin from the green alga Chlamydomonas reinhardtii.
The 1.5-A crystal structure of plastocyanin from the green alga Chlamydomonas reinhardtii.
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来自绿藻莱茵衣藻的质体蓝素的 1.5-A 晶体结构。
DOI：
10.1021/bi00091a005
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发表时间：
1993
期刊：
影响因子：
2.9
通讯作者：
Yeates,TO
中科院分区：
文献类型：
--
作者：
Redinbo,MR;Cascio,D;Choukair,MK;Rice,D;Merchant,S;Yeates,TO
摘要：来自绿色莱茵衣藻的质体蓝素的晶体结构已被确定为1.5-A分辨率，晶体学R因子为16.8%。质体蓝素是一种小的（98个氨基酸）蓝色铜结合蛋白，在产氧光合作用中催化电子从醌醇氧化酶复合物中的细胞色素/转移到光系统I中的P700+。莱茵衣藻质体蓝素是一种八链、反平行/3桶结构，具有一个铜原子，通过两个咪唑氮（来自His-37和His-87）、一个半胱氨酸硫（来自Cys-84）和一个甲硫氨酸硫（来自Met-92）以准四面体几何构型配位。该分子包含一个围绕Tyr-83的负电荷区域（推定的电子转移远端位点）和一个围绕His-87的完全疏水区域;这些区域被认为参与识别反应伴侣，以指导电子转移。莱茵衣藻质体蓝蛋白与其他已知结构的质体蓝蛋白相似，特别是来自浒苔和栅藻的绿色藻类质体蓝蛋白。在该蛋白质中已经确定了一种潜在的“通过键”的电子转移途径，该途径涉及Tyr-83的侧链、残基83和84之间的主链原子、Cys-84的侧链、铜原子和His-87的侧链。（97-99个氨基酸），氧化还原活性铜蛋白质，在产氧光合作用中的生化功能是催化电子从醌醇氧化酶复合物的还原cyt* 1/转移到P700+在光系统I中。在蓝铜蛋白中，质体蓝素可能是在结构水平上表征最好的[参见Sykes（1991）的综述]。蛋白质折叠成八链的β-夹心圆柱体（Colman等人，1978; Chazin和Wright，1988; Collyer等人，1990;摩尔等人，1991年）。含铜的活性位点，虽然没有溶剂暴露，是接近分子的表面，并协调到表面暴露的组氨酸（His-872）咪唑。其他三个配位基团是半胱氨酸（Cys-84）硫醇盐，甲硫氨酸（Met-92）硫醚和另一个组氨酸（His-37）咪唑。活性中心的几何形状为不规则或扭曲的四面体。这种变形可能是由多肽的折叠引起的，并且通过使Cu（I）形式稳定，导致蛋白质的相对高的中点电位（~ 370 mV）（加勒特等人，1986年）。
Revised Manuscript Received July 19, 1993® abstract: The crystal structure of plastocyanin from thegreen alga Chlamydomonas reinhardtii has been determined at 1.5-A resolution with a crystallographic R factor of 16.8%. Plastocyanin is a small (98 amino acids), blue copper-binding proteinthat catalyzes the transfer of electrons in oxygenic photosynthesis from cytochrome/in the quinol oxidase complex toP700+ in photosystem I. Chlamydomonas reinhardtii plastocyanin is an eight-stranded, antiparallel/3-barrel with a single copper atom coordinated in quasi-tetrahedral geometry by two imidazole nitrogens (from His-37 and His-87), a cysteine sulfur (from Cys-84), and a methionine sulfur (from Met-92). The molecule contains a region of negative charge surrounding Tyr-83 (the putative distant site of electron transfer) and an exclusively hydrophobic region surrounding His-87; these regions are thought to be involved in the recognition of reaction partners for the purpose of directing electron transfer. Chlamydomonas reinhardtii plastocyanin is similar to the other plastocyanins of known structure, particularly the green algal plastocyanins from Enteromorpha prolifera and Scenedesmus obliquus. A potential “through-bond” path of electron transfer has been identified in the protein that involves the side chain of Tyr-83, the main-chain atoms betweenresidues 83 and 84, the side chain of Cys-84, the copper atom, and the side chain of His-87.Plastocyanin is a small (97-99 amino acids), redox-active copper protein whose biochemicalfunction in oxygenic photosynthesis is the catalysis of electron transfer from reduced cyt* 1/of the quinol oxidase complex to P700+ in photosystem I. Of the blue copper proteins, plastocyanin is probably the best characterized at the structural level [see a review by Sykes (1991)]. The protein folds into an eight-stranded,/3-sandwich cylinder (Colman et al., 1978; Chazin & Wright, 1988; Collyer et al., 1990; Moore et al., 1991). The copper-containing active site, although not solvent-exposed, is close to the surface of the molecule and is coordinated to a surface-exposed histidinyl (His-872) imidazole. Thethree other coordinating groups are a cysteinyl (Cys-84) thiolate, a methioninyl (Met-92) thioether, and another histidinyl (His-37) imidazole. The geometry of the active site is an irregular or distorted tetrahedron. This distortion is presumably imposed by the folding of the polypeptide and, bystabilizing the Cu (I) form, is responsible for the relatively high midpoint potential (~ 370 mV) of the protein (Garrett et al., 1986).