光解一氧化碳细胞色素c氧化酶（细胞色素aa3）的时间分辨磁圆二色光谱
Time-resolved magnetic circular dichroism spectroscopy of photolyzed carbonmonoxy cytochrome c oxidase (cytochrome aa3).
作者信息
Goldbeck R A, Dawes T D, Einarsdóttir O, Woodruff W H, Kliger D S
机构信息
Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064.
出版信息
Biophys J. 1991 Jul;60(1):125-34. doi: 10.1016/S0006-3495(91)82036-7.
Nanosecond time-resolved magnetic circular dichroism (TRMCD) and time-resolved natural circular dichroism (TRCD) measurements of photolysis products of the CO complex of eukaryotic cytochrome c oxidase (CcO-CO) are presented. TRMCD spectra obtained at 100 ns and 10 microseconds after photolysis are diagnostic of pentacoordinate cytochrome a3Fe2+, as would be expected for simple photodissociation. Other time-resolved spectroscopies (UV-visible and resonance Raman), however, show evidence for unusual Fea3(2+) coordination after CO photolysis (Woodruff, W. H., O. Einarsdóttir, R. B. Dyer, K. A. Bagley, G. Palmer, S. J. Atherton, R. A. Goldbeck, T. D. Dawes, and D. S. Kliger. 1991. Proc. Nat. Acad. Sci. U.S.A. 88:2588-2592). Furthermore, time-resolved IR experiments have shown that photodissociated CO binds to CuB+ prior to recombining with Fea3(2+) (Dyer, R. B., O. Einarsdóttir, P. M. Killough, J. J. López-Garriga, and W. H. Woodruff. 1989. J. Am. Chem. Soc. 111:7657-7659). A model of the CcO-CO photolysis cycle which is consistent with all of the spectroscopic results is presented. A novel feature of this model is the coordination of a ligand endogenous to the protein to the Fe axial site vacated by the photolyzed CO and the simultaneous breaking of the Fe-imidazole(histidine) bond.
本文展示了真核细胞色素c氧化酶（CcO-CO）的CO复合物光解产物的纳秒时间分辨磁圆二色性（TRMCD）和时间分辨自然圆二色性（TRCD）测量结果。光解后100纳秒和10微秒时获得的TRMCD光谱可诊断五配位细胞色素a3Fe2+，这正如简单光解离所预期的那样。然而，其他时间分辨光谱学方法（紫外可见光谱和共振拉曼光谱）显示，CO光解后存在异常的Fea3(2+)配位现象（伍德拉夫，W. H.，O. 埃纳斯多蒂尔，R. B. 戴尔，K. A. 巴格利，G. 帕尔默，S. J. 阿瑟顿，R. A. 戈德贝克，T. D. 道斯，以及D. S. 克利格。1991年。《美国国家科学院院刊》88:2588 - 2592）。此外，时间分辨红外实验表明，光解离的CO在与Fea3(2+)重新结合之前先与CuB+结合（戴尔，R. B.，O. 埃纳斯多蒂尔，P. M. 基洛，J. J. 洛佩斯 - 加里加，以及W. H. 伍德拉夫。1989年。《美国化学会志》111:7657 - 7659）。本文提出了一个与所有光谱结果一致的CcO-CO光解循环模型。该模型的一个新颖之处在于，蛋白质内源性配体与光解的CO空出的Fe轴向位点配位，同时Fe-咪唑（组氨酸）键断裂。
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