Meunier B, Ortwein C, Brandt U, Rich P R
Glynn Laboratory of Bioenergetics, Department of Biology, University College London, Gower Street, London WC1E 6BT, U.K.
Biochem J. 1998 Mar 15;330 ( Pt 3)(Pt 3):1197-200. doi: 10.1042/bj3301197.
We describe effects of a mutation, Ile-67-->Asn, in subunit I of yeast cytochrome c oxidase on redox-linked protonation processes within the protein. The mutation lowers the midpoint potential of haem a and weakens its pH dependency, but has little effect on the potential of haem a3. The residue is close to a conserved glutamate (Glu-243) in the crystal structure. We propose that protonation of Glu-243 is redox-linked to haem a, that Asn-167 perturbs its pK and that redox-linked protonation in this location is essential for the catalytic reactions of the binuclear centre. These proposals are discussed in terms of a 'glutamate trap' mechanism for proton translocation in the haem/copper oxidases.
我们描述了酵母细胞色素c氧化酶亚基I中Ile-67→Asn突变对蛋白质内氧化还原相关质子化过程的影响。该突变降低了血红素a的中点电位并减弱了其pH依赖性，但对血红素a3的电位影响很小。在晶体结构中，该残基靠近一个保守的谷氨酸（Glu-243）。我们提出，Glu-243的质子化与血红素a发生氧化还原关联，Asn-167扰乱了其pK值，并且该位置的氧化还原相关质子化对于双核中心的催化反应至关重要。这些提议根据血红素/铜氧化酶中质子转运的“谷氨酸陷阱”机制进行了讨论。
