Ligand binding in a docking site of cytochrome C oxidase: a time-resolved step-scan Fourier transform infrared study.
Ligand binding in a docking site of cytochrome C oxidase: a time-resolved step-scan Fourier transform infrared study.
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细胞色素 C 氧化酶对接位点中的配体结合：时间分辨步进扫描傅里叶变换红外研究。
DOI：
10.1021/ja036107e
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发表时间：
2003
影响因子：
15
通讯作者：
C. Varotsis
中科院分区：
文献类型：
--
作者：
Constantinos Koutsoupakis;T. Soulimane;C. Varotsis
负责活化和催化小分子（O（2），NO）的酶的反应调节的描述需要识别配体运动进入结合位点和通过特定的通道和对接位点离开酶。本文采用时间分辨步进扫描傅里叶变换红外光谱法对T.嗜热菌，这是负责激活和还原的O（2）和NO，以获得洞察的配体结合中间体在环境温度下的结构。我们发现，解离后，光解的CO被捕获在位于血红素a的环A丙酸酯附近的配体对接位点内（3）。我们探测到的“对接”CO的2131 cm（-1）模式对应于MB的B（1）状态，并持续35 μ s。CO从对接位点释放后不会再与血红素a（3）Fe重组。我们的分析表明，这种行为反映了一种机制，其中血红素a（3）丙酸酯A环附近的蛋白质重组从对接位点释放的CO，并建立了一个短暂的障碍，抑制重组过程的血红素a（3）Fe几毫秒。当k（2）= 29.5 s（-1）时，发生与血红素a（3）的再结合。这些结果的影响，了解配体结合/逃逸的作用，通过对接网站和通道血红素铜氧化酶，因此，在呼吸。
The description of reaction regulation in enzymes responsible for activating and catalyzing small molecules (O(2), NO) requires identification of ligand movement into the binding site and out of the enzyme through specific channels and docking sites. We have used time-resolved step-scan Fourier transform infrared spectroscopy on CO-photolyzed cytochrome c oxidase ba(3) from T. thermophilus, which is responsible for the activation and reduction of both O(2) and NO, to gain insight into the structure of ligand-binding intermediates at ambient temperature. We show that, upon dissociation, the photolyzed CO becomes trapped within a ligand docking site located near the ring A propionate of heme a(3). The 2131 cm(-1) mode of the "docked" CO we have detected corresponds to the B(1) state of Mb and persists for 35 micros. The release of CO from the docking site is not followed by recombination to the heme a(3) Fe. Our analysis indicates that this behavior reflects a mechanism in which the protein near ring A of heme a(3) propionate reorganizes about the released CO from the docking site, and establishes a transient barrier that inhibits the recombination process to the heme a(3) Fe for a few milliseconds. Rebinding to heme a(3) occurs with k(2) = 29.5 s(-1). These results have implications for understanding the role of ligand binding/escape through docking sites and channels in heme-copper oxidases and, thus, in respiration.