Naqui A, Powers L, Lundeen M, Constantinescu A, Chance B
Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia 19104.
J Biol Chem. 1988 Sep 5;263(25):12342-5.
The role of zinc in beef heart cytochrome c oxidase has been studied by using x-ray absorption spectroscopy, zinc depletion and secondary structure predictions of subunits of beef heart cytochrome c oxidase. The stoichiometry of zinc in cytochrome oxidase has been determined in 35 different preparations and found to be one-half of copper (Cu:Zu = 2:1). Zinc is tightly bound to this enzyme and cannot be removed by dialysis against EDTA. However, zinc could be partially (up to 50%) depleted by treating the enzyme with either dipicolinic acid or by trypsin digestion. This partial depletion of zinc does not change the O2 uptake rate. X-ray absorption spectroscopy shows that the atom is in a distorted tetrahedral environment with mostly sulfur ligands. Since subunit VIa removed by the digestion removes about one-half the zinc, a possible binding site involves the two S sites present in that subunit with an appropriate folding in a structural role.
通过使用X射线吸收光谱法、锌耗竭法以及对牛心细胞色素c氧化酶亚基的二级结构预测，研究了锌在牛心细胞色素c氧化酶中的作用。在35种不同的制剂中测定了细胞色素氧化酶中锌的化学计量比，发现其为铜的一半（铜：锌 = 2:1）。锌与该酶紧密结合，不能通过用EDTA透析去除。然而，用二吡啶甲酸处理该酶或用胰蛋白酶消化可使锌部分（高达50%）耗竭。锌的这种部分耗竭不会改变氧气摄取率。X射线吸收光谱表明，该原子处于主要由硫配体构成的扭曲四面体环境中。由于消化去除的亚基VIa去除了约一半的锌，一个可能的结合位点涉及该亚基中存在的两个硫位点，并在结构上起到适当的折叠作用。
