Durham Bill, Millett Francis
Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR, USA.
Biochim Biophys Acta. 2012 Apr;1817(4):567-74. doi: 10.1016/j.bbabio.2011.08.012. Epub 2011 Sep 10.
This review describes the development and application of photoactive ruthenium complexes to study electron transfer and proton pumping reactions in cytochrome c oxidase (CcO). CcO uses four electrons from Cc to reduce O(2) to two waters, and pumps four protons across the membrane. The electron transfer reactions in cytochrome oxidase are very rapid, and cannot be resolved by stopped-flow mixing techniques. Methods have been developed to covalently attach a photoactive tris(bipyridine)ruthenium group [Ru(II)] to Cc to form Ru-39-Cc. Photoexcitation of Ru(II) to the excited state Ru(II*), a strong reductant, leads to rapid electron transfer to the ferric heme group in Cc, followed by electron transfer to Cu(A) in CcO with a rate constant of 60,000s(-1). Ruthenium kinetics and mutagenesis studies have been used to define the domain for the interaction between Cc and CcO. New ruthenium dimers have also been developed to rapidly inject electrons into Cu(A) of CcO with yields as high as 60%, allowing measurement of the kinetics of electron transfer and proton release at each step in the oxygen reduction mechanism.
本综述描述了光活性钌配合物在研究细胞色素c氧化酶（CcO）中的电子转移和质子泵浦反应方面的发展与应用。CcO利用来自细胞色素c的四个电子将O₂还原为两个水分子，并将四个质子泵过膜。细胞色素氧化酶中的电子转移反应非常迅速，无法通过停流混合技术解析。已开发出将光活性三（联吡啶）钌基团[Ru（II）]共价连接到细胞色素c上以形成Ru-39-细胞色素c的方法。Ru（II）光激发到激发态Ru（II*），一种强还原剂，会导致电子迅速转移到细胞色素c中的高铁血红素基团，随后以60,000s⁻¹的速率常数将电子转移到CcO中的Cu（A）。钌动力学和诱变研究已被用于确定细胞色素c与CcO之间相互作用的结构域。还开发了新的钌二聚体，以高达60%的产率将电子快速注入CcO的Cu（A），从而能够测量氧还原机制中每个步骤的电子转移和质子释放动力学。
