Diuba Artem V, Vygodina Tatiana V, Azarkina Natalia V, Arutyunyan Alexander M, Soulimane Tewfik, Vos Marten H, Konstantinov Alexander A
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory 1, Bld.40, Moscow 119992, Russia.
Materials and Surface Science Institute, University of Limerick, V94 T9PX, Ireland.
Biochim Biophys Acta Bioenerg. 2023 Apr 1;1864(2):148937. doi: 10.1016/j.bbabio.2022.148937. Epub 2022 Nov 18.
Bovine cytochrome c oxidase (CcO) contains two hemes, a and a, chemically identical but differing in coordination and spin state. The Soret absorption band of reduced aa-type cytochrome c oxidase consists of overlapping bands of the hemes a and a. It shows a peak at ∼444 nm and a distinct shoulder at ∼425 nm. However, attribution of individual spectral lineshapes to hemes a and a in the Soret is controversial. In the present work, we characterized spectral contributions of hemes a and a using two approaches. First, we reconstructed bovine CcO heme a spectrum using a selective Ca-induced spectral shift of the heme a. Second, we investigated photobleaching of the reduced Thermus thermophilus ba- and bovine aa-oxidases in the Soret induced by femtosecond laser pulses in the Q-band. The resolved spectra show splitting of the electronic B-, B-transitions of both reduced hemes. The heme a spectrum is shifted to the red relative to heme a spectrum. The ∼425 nm shoulder is mostly attributed to heme a.
牛细胞色素c氧化酶（CcO）含有两个血红素，即血红素a和血红素a₃，它们在化学性质上相同，但配位和自旋状态不同。还原型aa型细胞色素c氧化酶的Soret吸收带由血红素a和血红素a₃的重叠谱带组成。它在约444nm处有一个峰值，在约425nm处有一个明显的肩峰。然而，在Soret区域将各个光谱线形归因于血红素a和血红素a₃存在争议。在本研究中，我们使用两种方法表征了血红素a和血红素a₃的光谱贡献。首先，我们利用血红素a₃选择性的Ca诱导光谱位移重建了牛CcO血红素a的光谱。其次，我们研究了Q波段飞秒激光脉冲在Soret区域诱导的嗜热栖热菌ba型和牛aa型氧化酶还原态的光漂白。解析后的光谱显示两种还原型血红素的电子B-、B₃-跃迁发生了分裂。血红素a的光谱相对于血红素a₃的光谱向红端移动。约425nm处的肩峰主要归因于血红素a₃。
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