Structure and Function of the Reaction Center Complexes from Green Sulfur Bacteria

研究了绿色硫光合细菌Chlorobium tepidium的细胞色素(Cyt)C&lt；551&GT和与纯化的反应中心(RC)结合的Fe-S中心(CFA/CFB)在室温下的闪光诱导光学动力学。在551 nm处，闪光诱导的吸光度变化衰减，t_t；1/2&gt；为几百毫秒，1-甲氧基-5-甲基吩嗪甲基硫酸盐(MPMS)可加速其衰减。在蓝色区域，吸光度变化由依赖于mPMS的成分(Cyt)和非依赖于mPMS的成分(CFA/CFB)组成，其衰减的t_1/2&gt；为-400-650ms。苯基紫精(Em-360 mV)和甲基紫精(-440 mV)能有效地加速后者的衰变，而三喹酮(-540 mV)则不能有效地加速后者的衰变。Cytc的差光谱在551、-520和-420 nm处有负峰，在-440~-500 nm处有正上升。简写为：(B)Chl-(细菌)叶绿素；Cyt-细胞色素；光系统I的F_A、F_B和F_X-铁硫中心A、B和X；氯Ob的CF_A、CF_B和CF_X-F_A-、F_B和F_X-类Fe-S中心；mPMS-1-甲氧基-5-甲基吩氮甲基硫酸酯，PSI-光系统I；RC-反应中心

Flash-induced optical kinetics at room temperature of cytochrome (Cyt) c_<551> and an Fe-S center (CF_A/CF_B) bound to a purified reaction center (RC) complex from the green sulfur photosynthetic bacterium Chlorobium tepidum were studied. At 551 nm, the flash-induced absorbance change decayd with a t_<1/2> of several hundred ms, and the decay was accelerated by 1-methoxy-5-methylphenazinium methyl sulfate (mPMS). In the blue region, the absorbance change was composed of mPMS-dependent (Cyt) and mPMS-independent component (CF_A/CF_B) which decayd with a t_<1/2> of -400-650 ms. Decay of the latter was effectively accelerated by benzyl viologen (Em -360 mV) and methyl viologen (-440 mV), and less effectively by triquat (-540 mV). The difference spectrum of Cyt c had negative peaks at 551, -520 and -420 nm, with a positive rise a -440 to -500 nm. The difference spectrum of CF_A/CF_B resembled P430 of PSI,and had a broad negative peak at 430-435 nm.Abbreviations : (B) Chl- (bacterio) chlorophyll ; Cyt-cytochrome ; F_A, F_B and F_X-iron-sulfur center A,B and X of photosystem I ; CF_A, CF_B and CF_X-F_A-, F_B- and F_X-like Fe-S center of Chlorobium ; mPMS-1-methoxy-5-methylphenazinium methyl sulfate, PSI-Photosystem I ; RC-reaction center