Ortega J M, Dohse B, Oesterhelt D, Mathis P
Section de Bioénergétique (CNRS, URA 1290), Gif-sur-Yvette, France.
FEBS Lett. 1997 Jan 20;401(2-3):153-7. doi: 10.1016/s0014-5793(96)01440-8.
Electron transfer from the proximal heme c-559 to the primary donor P has been studied in reaction centers of the photosynthetic bacterium Rhodopseudomonas viridis in which the tyrosine residue L162 was replaced by threonine. In the wild type, when the two high-potential hemes of the tetraheme cytochrome are reduced before flash excitation, a rapid electron transfer (t1/2 = 190 ns) observed at ambient temperature disappears below 190 K. In the mutant, the reaction is partly maintained down to 8 K, leading to irreversible charge separation. The reaction rate is nearly temperature-independent between 294 K and 8 K (t1/2 approximately 450 ns). The different behavior of wild type and mutant reaction centers is attributed to differences in a network of water molecules, the freezing of which may block structural reorganizations associated with cytochrome oxidation, in the wild type but not in the mutant.
在光合细菌绿脓杆菌的反应中心中，已对从近端血红素c-559到初级供体P的电子转移进行了研究，其中酪氨酸残基L162被苏氨酸取代。在野生型中，当四血红素细胞色素的两个高电位血红素在闪光激发前被还原时，在环境温度下观察到的快速电子转移（t1/2 = 190纳秒）在190 K以下消失。在突变体中，该反应在低至8 K时仍部分保持，导致不可逆的电荷分离。反应速率在294 K和8 K之间几乎与温度无关（t1/2约为450纳秒）。野生型和突变体反应中心的不同行为归因于水分子网络的差异，在野生型中，水分子的冻结可能会阻止与细胞色素氧化相关的结构重组，但在突变体中则不会。
