Oxygen-linked equilibrium CuB-CO species in cytochrome ba3 oxidase from thermus thermophilus. Implications for an oxygen channel ar the CuB site.
Oxygen-linked equilibrium CuB-CO species in cytochrome ba3 oxidase from thermus thermophilus. Implications for an oxygen channel ar the CuB site.
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嗜热栖热菌细胞色素 ba3 氧化酶中的氧连接平衡 CuB-CO 物种。
DOI：
10.1074/jbc.m210293200
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
C. Varotsis
中科院分区：
文献类型：
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作者：
Konstantinos Koutsoupakis;S. Stavrakis;T. Soulimane;C. Varotsis
我们报告了 O(2) 在细胞色素 ba(3) 假定的 O(2) 通道中迁移及其对嗜热栖热菌细胞色素 ba(3) 的双核血红素 a(3)-Cu(B) 中心特性的影响的首次研究。 ba(3)-CO配合物的傅里叶变换红外光谱表明，在60-80μm O(2)存在的情况下，Cu(B)1+-C-O的nu(C-O)在2053 cm(-1)(配合物A)移动到2045 cm(-1)，并且在H(2)O/D(2)O交换和pH 6.5-9.0范围内保持不变。然而，血红素 a(3)-CO（复合物 B）的 C-O 拉伸模式的频率保持不变，但强度不变。配合物 A 的 nu(C-O) 变化导致 k(-2) 增加，从而提高 Cu(B) 与外源配体的亲和力。时间分辨步进扫描傅里叶变换红外差值光谱表明，在O(2)存在下，瞬态Cu(B)1+-CO配合物在pH 6.5下的衰减速率分别为30.4 s(-1)和28.3 s(-1)。同样，与血红素 a(3) 的重新结合受到轻微影响，并且在 O(2) 存在的情况下，在 k(2) = 26.3 s(-1) 和 24.6 s(-1) 时发生。这些结果提供了确凿的证据，证明在细胞色素ba(3)中，配体递送通道位于Cu(B)位点，这是配体进入血红素a(3)口袋的入口。我们认为，O(2) 通道的特性不仅限于促进配体扩散到活性位点，还可以扩展到控制 ba(3) 与 O(2) 和 NO 反应的动力学和反应性。
We report the first study of O(2) migration in the putative O(2) channel of cytochrome ba(3) and its effect to the properties of the binuclear heme a(3)-Cu(B) center of cytochrome ba(3) from Thermus thermophilus. The Fourier transform infrared spectra of the ba(3)-CO complex demonstrate that in the presence of 60-80 micro m O(2), the nu(C-O) of Cu(B)1+-C-O at 2053 cm(-1) (complex A) shifts to 2045 cm(-1) and remains unchanged in H(2)O/D(2)O exchanges and in the pH 6.5-9.0 range. The frequencies but not the intensities of the C-O stretching modes of heme a(3)-CO (complex B), however, remain unchanged. The change in the nu(C-O) of complex A results in an increase of k(-2), and thus in a higher affinity of Cu(B) for exogenous ligands. The time-resolved step-scan Fourier transform infrared difference spectra indicate that the rate of decay of the transient Cu(B)1+-CO complex at pH 6.5 is 30.4 s(-1) and 28.3 s(-1) in the presence of O(2). Similarly, the rebinding to heme a(3) is slightly affected and occurs with k(2) = 26.3 s(-1) and 24.6 s(-1) in the presence of O(2). These results provide solid evidence that in cytochrome ba(3), the ligand delivery channel is located at the Cu(B) site, which is the ligand entry to the heme a(3) pocket. We suggest that the properties of the O(2) channel are not limited to facilitating ligand diffusion to the active site but are extended in controlling the dynamics and reactivity of the reactions of ba(3) with O(2) and NO.