LOB, CNRS, INSERM, Ecole Polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France.
LOB, CNRS, INSERM, Ecole Polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France.
Biochim Biophys Acta Bioenerg. 2021 May 1;1862(5):148385. doi: 10.1016/j.bbabio.2021.148385. Epub 2021 Jan 29.
Cytochrome bc complexes are energy-transducing enzymes and key components of respiratory electron chains. They contain Rieske 2Fe2S proteins that absorb very weakly in the visible absorption region compared to the heme cofactors of the cytochromes, but are known to yield photoproducts. Here, the photoreactions of isolated Rieske proteins from the hyperthermophilic bacterium Aquifex aeolicus are studied in two redox states using ultrafast transient fluorescence and absorption spectroscopy. We provide evidence, for the first time in iron‑sulfur proteins, of very weak fluorescence of the excited state, in the oxidized as well as the reduced state. The excited states of the oxidized and reduced forms decay in 1.5 ps and 30 ps, respectively. In both cases they give rise to product states with lifetimes beyond 1 ns, reflecting photo-reduction of oxidized centers as well as photo-oxidation of reduced centers. Potential reaction partners are discussed and studied using site-directed mutagenesis. For the reduced state, a nearby disulfide bridge is suggested as an electron acceptor. The resulting photoproducts in either state may play a role in photoactivation processes.
细胞色素 bc 复合物是能量转换酶，也是呼吸电子链的关键组成部分。它们包含 Rieske 2Fe2S 蛋白，与细胞色素的血红素辅基相比，它们在可见光吸收区域的吸收非常弱，但已知会产生光产物。在这里，使用超快瞬态荧光和吸收光谱研究了来自嗜热菌 Aquifex aeolicus 的分离 Rieske 蛋白在两种氧化还原态下的光反应。我们首次在铁硫蛋白中提供了证据，证明激发态的荧光非常微弱，无论是在氧化态还是还原态下都是如此。氧化态和还原态的激发态分别在 1.5 ps 和 30 ps 内衰减。在这两种情况下，它们都会产生寿命超过 1 ns 的产物态，这反映了氧化中心的光还原以及还原中心的光氧化。使用定点突变研究了潜在的反应伙伴。对于还原态，建议附近的二硫键作为电子受体。在任一状态下产生的光产物都可能在光激活过程中发挥作用。
