Evidence for Fast Electron Transfer between the High-Spin Haems in Cytochrome bd-I from Escherichia coli.
Evidence for Fast Electron Transfer between the High-Spin Haems in Cytochrome bd-I from Escherichia coli.
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DOI：
10.1371/journal.pone.0155186
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Borisov VB
中科院分区：
文献类型：
--
作者：
Siletsky SA;Rappaport F;Poole RK;Borisov VB
细胞色素bd-I是大肠杆菌O2依赖性呼吸链中三种产生质子动力的醌醇氧化酶之一。它包含一个低自旋血红素（b558）和两个高自旋血红素（b595和d）作为氧化还原活性辅因子。为了研究闪光灯诱导的蛋白质内反向电子转移（所谓的“电子回流”），在单电子还原的（b5583+b5953+d2+-CO）细胞色素bd-I和完全还原的（b5582+b5952+d2+-CO）氧化酶中，从亚铁血红素d光解CO。与完全还原的细胞色素bd-I相比，单电子还原氧化酶在延迟时间为1.5 μs和200 ns时的瞬态光谱有明显的不同。两个光谱之间的差异可以建模为在3-4%的细胞色素bd-I群体中从血红素d到血红素b595的电子转移。因此，在单电子还原的细胞色素bd-I中，由血红素d的CO光解诱导的血红素间电子回流反应包括两个动力学上不同的阶段：先前未注意到的在0.2-1.5 μs内从血红素d到血红素b595的快速电子转移和τ ~16 μs的较慢的明确的电子平衡。这项工作的主要新发现是在200 ns处缺乏电子转移。
Cytochrome bd-I is one of the three proton motive force-generating quinol oxidases in the O2-dependent respiratory chain of Escherichia coli. It contains one low-spin haem (b558) and the two high-spin haems (b595 and d) as the redox-active cofactors. In order to examine the flash-induced intraprotein reverse electron transfer (the so-called ''electron backflow''), CO was photolyzed from the ferrous haem d in one-electron reduced (b5583+b5953+d2+-CO) cytochrome bd-I, and the fully reduced (b5582+b5952+d2+-CO) oxidase as a control. In contrast to the fully reduced cytochrome bd-I, the transient spectrum of one-electron reduced oxidase at a delay time of 1.5 μs is clearly different from that at a delay time of 200 ns. The difference between the two spectra can be modeled as the electron transfer from haem d to haem b595 in 3–4% of the cytochrome bd-I population. Thus, the interhaem electron backflow reaction induced by photodissociation of CO from haem d in one-electron reduced cytochrome bd-I comprises two kinetically different phases: the previously unnoticed fast electron transfer from haem d to haem b595 within 0.2–1.5 μs and the slower well-defined electron equilibration with τ ~16 μs. The major new finding of this work is the lack of electron transfer at 200 ns.