Intramolecular electron transfer and conformational changes in cytochrome c oxidase.
Intramolecular electron transfer and conformational changes in cytochrome c oxidase.
复制标题
细胞色素c氧化酶的分子内电子转移和构象变化。
DOI：
10.1021/bi00002a014
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发表时间：
1995
期刊：
影响因子：
2.9
通讯作者：
Sucheta,A
中科院分区：
文献类型：
--
作者：
Einarsdóttir,O;Georgiadis,KE;Sucheta,A
摘要：研究了部分和完全还原CO结合的细胞色素氧化酶衍生物的光解中间体。门控光谱多道分析仪被用来收集可见和近红外瞬态差异光谱的时间尺度从纳秒到毫秒。用奇异值分解法结合全局指数拟合法对光谱进行了分析。对混合价CO络合物瞬态差谱的全局分析表明，存在五种中间体，其表观寿命分别为1.4 µ $、4.8 µ $、76.7 µ $、10.6 ms和21.6 ms。在此基础上，测定了中间体的吸收光谱。第一步，也存在于完全还原的酶，是由于在细胞色素的构象变化。与第二步相关的光谱变化是类似的预期为1：1的电子转移从细胞色素作为细胞色素a，除了在480和550 nm之间的吸光度较高。与该步骤相关的实验光谱变化（a2+减去a3+）减去（a2+减去a3+）与计算的光谱变化（a2+ Cua+减去a3+ Cua 2+）减去（a2 + Cub+减去a3 + Cub 2+）的比较允许在480-550 nm区域提取Cua 2+的吸收光谱。与第三步相关的光谱变化与细胞色素a的氧化一致。在相同的时间尺度上，830 nm波段的减少表明电子受体是Cu。数据还
Revised Manuscript Received November 1, 1994® abstract: The photolysis intermediates of partially and fully reduced CO-bound cytochrome oxidase derivatives were investigated. A gated optical spectrometric multichannel analyzer was used to collect visible and near-infrared transient difference spectra on time scales from nanoseconds to milliseconds. The spectra were analyzed by a singular value decomposition method combined with a global exponential fitting procedure. Global analysis of the mixed-valence COcomplex transient difference spectra shows that five intermediates are present with apparent lifetimes of 1.4 µ $, 4.8 µ $, 76.7 µ&, 10.6 ms, and 21.6 ms. The data were fitted to a kinetic model involving a sequential pathway with accompanying equilibria. On the basis of this mechanism, the absorption spectra of the intermediates were determined. The first step, also present in the fully reduced enzyme, is attributed to a conformational change at cytochrome as.The spectral changes associated with the second step are similar to those expected for 1: 1 electron transfer from cytochrome as to cytochrome a, except for a higher absorbance between 480 and 550 nm. A comparison of the experimental spectral change associated with this step,(a2+ minus a3+) minus (as2+ minus as3+), and the calculated spectral change,(a2+ Cua+ minus a3+ Cua2+) minus {as2+ Cub+ minus ii33+ Cub2+), allowed extraction of the absorbance spectrum of Cua2+ in the 480—550 nm region. The spectral change associated with the third step is consistent with the oxidation of cytochrome a. A decrease in the 830 nm band on the same time scale indicates that the electron acceptor isCua-The data also