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

在绿色硫磺细菌Chlorobium tepidum的反应中心复合体(PS-C)中，A0和三个Fe-S团簇作用于电子转移链的受体侧，两个Cytc-551分子作用于给体侧。从多次闪光诱导光谱中，我们没有发现在主电子转移链中有任何可能的苯二酚的作用。在给体侧，第一次闪光后P840^+的还原速率与第二次闪光后的P840^+的还原速率不同，这可以用功能等效的两个Cyt c-551模型来充分解释。从PS-C的差谱确定了三个Fe-S团簇的功能，从P840^+的再还原速率估算了P840^+与三个Fe-S团簇之间的电荷复合速率和电子泄漏到反应介质的速率。对结果的分析表明，暴露最严重的Fe-S星团的E0值并不是三个星团中最高的。从冬虫夏草中分离纯化了四种铁氧还蛋白(FD)。所有这些FD都支持很高的NADP^+光还原速率，尽管它们的亲和力不同，但在PS-C和菠菜FNR的存在下。运动螺杆菌RC(PS-H)用洗涤剂溶解，并通过蔗糖密度离心法和层析法进行部分纯化。PS-H制剂含有多个多肽，具有较低的FD还原活性，对氧敏感。从该菌中分离纯化出两种Fd。其中一个与PS-C有高亲和力，另一个与PS-C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.