FUNCTION OF HELIOBACTERIA- AND GREEN SULFUR BACTERIA-TYPE REACTION CENTERS

在绿硫菌的反应中心配合物（PS-C）中，A_0和3个Fe-S簇作用于电子传递链的受体侧，两个cyt c-551分子作用于供体侧。从多重闪光诱导光谱中，我们没有发现醌在主电子传递链上起作用的任何可能性。在供体侧，P840^+在第一次闪光后的还原率与第二次闪光后的还原率不同，这可以用功能等效的2 cyt c-551模型充分解释。从PS-C在1^<st>、2^<和>以及3^<rd>闪变后的光谱差异，证实了3个Fe-S簇的功能，证实了奎宁在电子传递链中没有参与到受体侧；从P840^+的还原速率，估计了P840^+与3个Fe-S簇之间的电荷重组速率和电子泄漏到反应介质的速率。分析结果表明，暴露最多的Fe-S簇的E_0值并不是3个簇中最高的。从雪蚤中分离得到4个铁氧化还原蛋白。所有这些Fd都支持非常高的NADP^+光还原率，尽管它们的亲和性不同。从移动Heliobacillus mobilis中提取的RC （PS-H）用洗涤剂溶解，并通过蔗糖密度离心和层析进行部分纯化。PS-H含有多种多肽，具有较低的fd还原活性，对氧敏感。从细菌中纯化出两个Fd。其中一个与PS-C具有高亲和力，另一个与PS-C具有低亲和力。

In the reaction center complex (PS-C) from the green sulfur bacterium Chlorobium tepidum, A_0 and three Fe-S clusters function on the accepter side of the electron transfer chain and two molecules of cyt c-551 on the donor side. From multiple-flash-induced spectroscopy, we could not find any possibilities of functioning of quinone in the main electron transfer chain. On the donor side, the reduction rate of P840^+ after the first flash differed from that after the second flash, which was adequately explained by a functionally equivalent two cyt c-551 model. From the difference spectra of PS-C after the 1^<st>, 2^<nd> and the 3^<rd> flash, functioning of three Fe-S clusters was confirmed, corroborating the non-involvement of quinines on the acceptor side in the electron transfer chain, From the rereduction rates of P840^+, the rates of charge recombination between P840^+ and three Fe-S clusters and those of the leak of electron to the reaction mdeium were estimated. Analyses of the results indicate that the E_0 value of the most exposed Fe-S cluster is not the highest among the three. Four ferredoxins (Fd) were purified from C.tepidum. All of these Fd supported very high rate of NADP^+ photoreduction in the presence of PS-C from C.repidum and FNR from spinach, although their affinities differ each other.RC (PS-H) from Heliobacillus mobilis was solubilized with a detergent, and partially purified by sucrosedensity centrifugation, and by chromatography. The PS-H preparation contained several polypeptides, showed a low Fd-reducing activity, and was sensitive to oxygen. Two Fd were purified from the bacterium. One of them had high affinity with PS-C and the other low affinity.