Spectroscopic studies of green-bacterial reaction center

绿菌反应中心的光谱研究

• 批准号: 08044223
• 负责人: SAKURAI Hidehiro
• 金额: $ 5.57万
• 依托单位: Waseda University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for international Scientific Research
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08044223/
• 关键词: photosynthesis; reaction center; green sulfur bacteria; cytochrome; iron-sulfur cluster; flash-absorption spectroscopy; menaquinone-7; Fe-Sセンター; 閃光分光

Electron transfer kinetics in the reaction center (Re) complex from the green sulfur bacterium Chlorobium tepidum which binds two cytochrome c (cyt c) were studied by flash-absorption spectroscopy. Photooxidized P84O^+ was reduced 95% and 80% after 1 ms by cyt c with t^<1/2> of about 65 mus and 100 muz s after the 1st and the 2nd flashes, respectively . The observed rates, the establishment of redox equilibrium after each flash and the total amount of photooxidizable cyt c are consistent with the presence of 2 equivalent cyt c per photooxidizable P840. The data were well fitted assuming a midpoint potential difference of -53 mV for electron transfer from one cyt c to P8404^+, * Em being independent of the oxidation state of the other cyt c. These observations support a model with 2 monoheme cyt c which are symmetrically arranged around the RC core. The purified RC complex binds 0.6-1.2 menaquinone-7 (MQ) . However, no transient signal due to MQ could be observed between 360 and 450 nm in the time window from 10 ns to 4 mu s. On the acceptor side, purified RC can stably hold up to 3 electrons in the mu s time range.However, after the 4th flash, a charge recombination reaction with t^<1/2> of 20 ns was first observed. From our data, there is no evidence for involvement of MQ in charge separation in the RC of green sulfur bacteria.

用闪光吸收光谱法研究了绿色硫细菌Chlorobium tepidum与两个细胞色素c（cyt c）结合的反应中心（Re）复合物的电子转移动力学。在第一次和第二次闪光后，光氧化的P84 O ^+在1 ms后被cyt c还原95%和80%，t^<1/2>分别约为65 μ s和100 μ z s。观察到的速率、每次闪光后氧化还原平衡的建立和可光氧化的cyt c的总量与每个可光氧化的P840存在2当量cyt c一致。假设电子从一个cyt c转移到P8404^+的中点电位差为-53 mV，* Em与另一个cyt c的氧化态无关，则数据拟合良好。这些观察结果支持了一个模型，2个单血红素细胞色素c对称地排列在RC核心周围。纯化的RC复合物结合0.6-1.2甲基萘醌-7（MQ）。然而，在10 ns至4 μ s的时间窗口内，在360和450 nm之间没有观察到由于MQ引起的瞬态信号。在受体侧，纯化的RC可以在μ s的时间范围内稳定地容纳多达3个电子，然而，在第四次闪光后，首次观察到t^1/2为20 ns的电荷复合反应。从我们的数据来看，没有证据表明MQ参与了绿色硫细菌RC中的电荷分离。

项目成果

Seo, D., Kusumoto, N., Sakurai, H., Brettel, K., Setif, P.: "Proceedings of the XIth International Conference on Photosynthesis (Garab, G.Ed.)" Kluwer Academic Publishers, Dordrecht, 4 (1998)

Seo, D.、Kusumoto, N.、Sakurai, H.、Brettel, K.、Setif, P.：“第 XI 届国际光合作用会议论文集（Garab，G.Ed.）” Kluwer 学术出版社，多德雷赫特，4

Noguchi,T.,Kusumoto,N.,Inoue,Y.,Sakurai,H.: "Electronic and vibrational structure of the radical cation of P840 in the putative homodimeric reaction center from chlorobium tepidum as studied by FTIR spectroscopy" Biochemistry. 35. 15428-15435 (1996)

Noguchi，T.，Kusumoto，N.，Inoue，Y.，Sakurai，H.：“通过 FTIR 光谱研究来自温绿草的推定同二聚反应中心 P840 自由基阳离子的电子和振动结构”生物化学。

Seo, D., Kusumoto, N., Sakurai, H.Brettel, K., Setif, P.: Proceedings of the XIth International Conference on Photosynthesis (Garab, G.Ed.). Kluwer Academic Publishers, Dordrecht, 4 (1998)

Seo, D.、Kusumoto, N.、Sakurai, H.Brettel, K.、Setif, P.：第十一届国际光合作用会议论文集（Garab，G.Ed.）。

Sakurai, H., Kusumoto, N.: "Electronic and vibrational structure of the radical cation of P840 in the putative homodimeric reaction center from Chlorobium tepidum as studied by FTIR spectroscopy" Biochemistry. 35・48. 15428-15435 (1996)

Sakurai, H., Kusumoto, N.：“通过 FTIR 光谱研究的温绿球菌推定同二聚反应中心中 P840 自由基阳离子的电子和振动结构”生物化学 15428-15435 (1996)。