Grossmann J G, Ingledew W J, Harvey I, Strange R W, Hasnain S S
Molecular Biophysics Group, Daresbury Laboratory, Warrington, Cheshire, U.K.
Biochemistry. 1995 Jul 4;34(26):8406-14. doi: 10.1021/bi00026a023.
Rusticyanin, a blue copper protein, possessing the highest redox potential among this class of proteins and a high stability at acidic pH reveals homology with the C-terminal end of the other single copper containing blue proteins and an interesting homology to parts of the blue copper domain of the multi-copper proteins such as the nitrite reductases. Extended X-ray absorption fine structure (EXAFS) data at pH 2.0 reveal that Cu is ligated to two His and a Cys in the inner coordination sphere, similar to other blue copper centers. Modeling studies suggest that His85 is the ligating histidine from the N-terminal end. Its neighboring residue is a serine rather than the asparagine found in all known blue Cu proteins. The high stability of the copper site may arise in part due to this substitution. The Cu binding site is surrounded by aromatic residues which may provide further protection for the metal in an acidic environment. In addition, the high number of solvent-exposed uncompensated lysine residues is likely to be of functional relevance under low pH conditions. EXAFS data show a very small change (relative to azurin) in the copper site upon reduction, consistent with a more constrained copper center in rusticyanin compared to azurin and a higher redox potential.
乡村蓝蛋白是一种蓝色铜蛋白，在这类蛋白中具有最高的氧化还原电位，并且在酸性pH条件下具有高稳定性。它与其他含单铜蓝色蛋白的C末端存在同源性，并且与多铜蛋白（如亚硝酸还原酶）的蓝色铜结构域的部分区域存在有趣的同源性。在pH 2.0条件下的扩展X射线吸收精细结构（EXAFS）数据表明，铜在内层配位球中与两个组氨酸和一个半胱氨酸配位，这与其他蓝色铜中心类似。建模研究表明，His85是来自N末端的配位组氨酸。它的相邻残基是丝氨酸，而不是在所有已知蓝色铜蛋白中发现的天冬酰胺。铜位点的高稳定性可能部分归因于这种取代。铜结合位点被芳香族残基包围，这可能在酸性环境中为金属提供进一步的保护。此外，大量暴露于溶剂的未补偿赖氨酸残基在低pH条件下可能具有功能相关性。EXAFS数据表明，与天青蛋白相比，还原后铜位点的变化非常小（相对于天青蛋白），这与乡村蓝蛋白中铜中心比天青蛋白更受限制以及更高的氧化还原电位一致。
