Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, C1428EHA-Buenos Aires, Argentina.
Phys Chem Chem Phys. 2011 Oct 28;13(40):18088-98. doi: 10.1039/c1cp21925a. Epub 2011 Sep 15.
The subunit II of the caa(3) oxygen reductase from Rhodothermus marinus contains, in addition to the Cu(A) center, a c-type heme group in the cytochrome c domain (Cyt-D) that is the putative primary electron acceptor of the enzyme. In this work we have combined surface-enhanced resonance Raman (SERR) spectroelectrochemistry, molecular dynamics (MD) simulations and electron pathway calculations to assess the most likely interaction domains and electron entry/exit points of the truncated Cyt-D of subunit II in the reactions with its electron donor, HiPIP and electron acceptor, Cu(A). The results indicate that the transient interaction between Cyt-D and HiPIP relies upon a delicate balance of hydrophobic and polar contacts for establishing an optimized electron transfer pathway that involves the exposed edge of the heme group and guaranties efficient inter-protein electron transfer on the nanosecond time scale. The reorganization energy of ca. 0.7 eV was determined by time-resolved SERR spectroelectrochemistry. The intramolecular electron transfer pathway in integral subunit II from Cyt-D to the Cu(A) redox center most likely involves the iron ligand histidine 20 as an electron exit point in Cyt-D.
从海洋红假单胞菌中分离出的 caa(3) 氧还原酶亚基 II 除了包含 Cu(A) 中心外，在细胞色素 c 结构域 (Cyt-D) 中还含有一个 c 型血红素基团，它是该酶的假定的最初电子受体。在这项工作中，我们结合表面增强共振拉曼 (SERR) 光谱电化学、分子动力学 (MD) 模拟和电子路径计算，以评估截断的亚基 II Cyt-D 与电子供体 HiPIP 和电子受体 Cu(A) 反应时最可能的相互作用结构域和电子进入/退出点。结果表明，Cyt-D 与 HiPIP 之间的瞬态相互作用依赖于疏水性和极性接触之间的微妙平衡，以建立涉及血红素基团暴露边缘的优化电子转移途径，并保证在纳秒时间尺度上有效的蛋白质间电子转移。通过时间分辨 SERR 光谱电化学确定了约 0.7 eV 的重组能。完整亚基 II 中 Cyt-D 到 Cu(A) 氧化还原中心的分子内电子转移途径很可能涉及 Cyt-D 中的铁配体组氨酸 20 作为电子出口点。
