Stellacyanin. Studies of the metal-binding site using x-ray absorption spectroscopy.
Stellacyanin. Studies of the metal-binding site using x-ray absorption spectroscopy.
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星花苷。
DOI：
10.1016/s0006-3495(82)84559-1
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发表时间：
1982
影响因子：
3.4
通讯作者：
Chance,B
中科院分区：
文献类型：
--
作者：
Peisach,J;Powers,L;Blumberg,WE;Chance,B
Stellacyanin是一种分子量约为20，000的粘蛋白，在蓝色或I型位点含有一个铜原子。金属离子可以以Cu（II）和Cu（I）氧化还原态存在。另一种蓝铜蛋白质质体蓝蛋白中的金属结合位点含有一个半胱氨酰、一个甲硫氨酰和两个咪唑基残基（Colman等人，1978年）。自然[伦敦]。272：319-324.），但在星花青蛋白中不存在完全类似的位点，因为它缺乏甲硫氨酸。用X射线边吸收和扩展X射线吸收精细结构（EXAFS）研究了星花青苷中铜的配位作用。本文介绍了一种新的、非常保守的数据分析方法，它表明在氧化态[Cu（II）]蛋白质的第一配位壳层中有两个氮原子，在还原态[Cu（I）]蛋白质中有一个氮原子，这些氮原子具有正常的Cu-N距离：1.95-2.05 A.在这两种氧化还原状态下，都有一个或两个硫原子与铜配位，从目前的数据中无法确定确切的数量。在氧化状态下的Cu-S的距离是在plastocyanin中发现的短键和那些发现在附近的tetraphthalic铜模型化合物之间的中间。在-140 ℃以上，蛋白质发生辐射损伤。在室温下，氧化的蛋白质在X射线束中以0.25%/s的速率被修饰。
Stellacyanin is a mucoprotein of molecular weight approximately 20,000 containing one copper atom in a blue or type I site. The metal ion can exist in both the Cu(II) and Cu(I) redox states. The metal binding site in plastocyanin, another blue copper protein, contains one cysteinyl, one methionyl, and two imidazoyl residues (Colman et al. 1978. Nature [Lond.]. 272:319–324.), but an exactly analogous site cannot exist in stellacyanin as it lacks methionine. The copper coordination in stellacyanin has been studied by x-ray edge absorption and extended x-ray absorption fine structure (EXAFS) analysis. A new, very conservative data analysis procedure has been introduced, which suggests that the there are two nitrogen atoms in the first coordination shell of the oxidized [Cu(II)] protein and one in the reduced [Cu(I)] protein; these N atoms have normal Cu--N distances: 1.95–2.05 A. In both redox states there are either one or two sulfur atoms coordinating the copper, the exact number being indeterminable from the present data. In the oxidized state the Cu--S distance is intermediate between the short bond found in plastocyanin and those found in near tetragonal copper model compounds. Above -140 degree C, radiation damage of the protein occurs. At room temperature the oxidized proteins is modified in the x-ray beam at a rate of 0.25%/s.