Koyama Kohei, Suzuki Hiroyuki, Noguchi Takumi, Akimoto Seiji, Tsuchiya Tohru, Mimuro Mamoru
Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan.
Biochim Biophys Acta. 2008 Apr;1777(4):369-78. doi: 10.1016/j.bbabio.2008.01.009. Epub 2008 Feb 11.
The oxygen-evolving reactions of the thylakoid-lacking cyanobacterium Gloeobacter violaceus PCC 7421 were compared with those of Synechocystis sp. PCC 6803. Four aspects were considered: sequence conservation in three extrinsic proteins for oxygen evolution, steady-state oxygen-evolving activity, charge recombination reactions, i.e., thermoluminescence and oscillation patterns of delayed luminescence on a second time scale and delayed fluorescence on the nanosecond time scale at -196 degrees C. Even though there were significant differences between the amino acid sequences of extrinsic proteins in G. violaceus and Synechocystis sp. PCC 6803, the oxygen-evolving activities were similar. The delayed luminescence oscillation patterns and glow curves of thermoluminescence were essentially identical between the two species, and the nanosecond delayed fluorescence spectral profiles and lifetimes were also very similar. These results indicate clearly that even though the oxygen-evolving reactions are carried out in the periplasm by components with altered amino acid sequences, the essential reaction processes for water oxidation are highly conserved. In contrast, we observed significant changes on the reduction side of photosystem II. Based on these data, we discuss the oxygen-evolving activity of G. violaceus.
将缺乏类囊体的蓝细菌紫球藻（Gloeobacter violaceus）PCC 7421的放氧反应与集胞藻（Synechocystis sp.）PCC 6803的放氧反应进行了比较。考虑了四个方面：参与放氧的三种外在蛋白的序列保守性、稳态放氧活性、电荷复合反应，即-196℃下热发光以及第二次时间尺度上延迟发光的振荡模式和纳秒时间尺度上延迟荧光的振荡模式。尽管紫球藻和集胞藻PCC 6803的外在蛋白氨基酸序列存在显著差异，但放氧活性相似。两种藻的延迟发光振荡模式和热发光辉光曲线基本相同，纳秒延迟荧光光谱轮廓和寿命也非常相似。这些结果清楚地表明，尽管放氧反应是由氨基酸序列改变的组分在周质中进行的，但水氧化的基本反应过程高度保守。相比之下，我们在光系统II的还原侧观察到了显著变化。基于这些数据，我们讨论了紫球藻的放氧活性。
