Peisach J, Powers L, Blumberg W E, Chance B
Biophys J. 1982 Jun;38(3):277-85. doi: 10.1016/S0006-3495(82)84559-1.
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.
星蓝蛋白是一种分子量约为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)两种氧化还原状态存在。质体蓝素是另一种蓝色铜蛋白，其金属结合位点包含一个半胱氨酰基、一个甲硫氨酰基和两个咪唑基残基（科尔曼等人，1978年，《自然》[伦敦]。272:319 - 324），但星蓝蛋白中不可能存在完全类似的位点，因为它缺乏甲硫氨酸。通过X射线边缘吸收和扩展X射线吸收精细结构（EXAFS）分析研究了星蓝蛋白中的铜配位情况。引入了一种新的、非常保守的数据分析程序，该程序表明氧化态[Cu(II)]蛋白的第一配位层中有两个氮原子，还原态[Cu(I)]蛋白中有一个氮原子；这些氮原子具有正常的Cu - N距离：1.95 - 2.05埃。在两种氧化还原状态下，都有一个或两个硫原子与铜配位，确切数量根据目前的数据无法确定。在氧化态下，Cu - S距离介于质体蓝素中发现的短键和近四方铜模型化合物中发现的短键之间。在-140摄氏度以上，蛋白质会发生辐射损伤。在室温下，氧化态蛋白在X射线束中的修饰速率为0.25%/秒。
