A molecular mechanism for copper transportation to tyrosinase that is assisted by a metallochaperone, caddie protein

我们先前已经确定，酪氨酸酶在Cu（II）浸泡下的晶体结构与一种被称为“caddie”的蛋白质复合物中，显示出在催化中心有两个铜离子。我们在球童蛋白中观察到两个铜结合位点，推测与球童蛋白结合的铜可能被转运到酪氨酸酶催化中心。本研究在1.16 ~ 1.58 A的分辨率下，测定了通过改变铜离子浸泡时间制备的酪氨酸酶与球体的晶体结构，以及酪氨酸酶与一些不具有或很少具有酪氨酸酶激活能力的突变体球体的结构。基于这些结构，我们提出了一种将两个铜离子运输到酪氨酸酶催化中心的分子机制，该机制在球体作为金属伴侣的辅助下进行。

The Cu(II)-soaked crystal structure of tyrosinase in a complex with a protein, designated “caddie”, which has previously determined by us, displays to possess two copper ions at the catalytic center. We observed two copper-binding sites in the caddie protein, speculating that the copper bound to caddie may be transported to the tyrosinase catalytic center. In the present study, at the 1.16 to 1.58 A resolution, we determined the crystal structures of tyrosinase complexed with a caddie prepared by altering the soaking time of the copper ion and the structures of tyrosinase complexed with a few mutants of a caddie which displays no or little ability to activate tyrosinase. Based on these structures, we propose a molecular mechanism to transport two copper ions to the tyrosinase catalytic center, which is assisted by a caddie as a metallochaperone.