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THE REALITIES OF HOMODIMER-TYPE REACTION CENTER FROM GREEN SULFUR BACTERIA AND ITS OXYGEN SUSCEPTIBILITY

绿硫菌同源二聚体型反应中心的真实性及其氧敏感性

基本信息

批准号：
10640640
负责人：
SAKURAI Hidehiro
金额：
$ 2.11万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

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 found that cyt c-551 was reduced with half-lives of about 60 and 100 μs after the first and the second flash, respectively. These behaviors of cyt c-551 are explained by a model of two functionally equivalent cyt c, and are consistent with a homodimeric model on the donor side. The above apparently different rates are explained by the fact that after the first flash, two cyt c-551 are available for electron donation to P840, while only one is available in the majority of PS-C after the second flash. When PS-C was exposed to air, a rapid inactivation occurred on the acceptor side, the actual site of inactivation remaining to be investigated.Four ferredoxins (Fds) of 2[4Fe-4S] type were purified from C.tepidum. In the presence of PS-C and FNR from spinach, all of them supported efficient NADP^+ reduction. Fds from green sulfur bacteria were reported to be extremely sensitive to oxygen. However, these Fds from C.tepidum was relatively insensitive to oxygen, and inactivated by only 10-15% by storage under aerobic conditions at 4℃. We have purified two Fds from Heliobacillus mobilis. One of them was extremely sensitive to oxygen, but the other relatively insensitive to oxygen as are Fds from C.tepidum.

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。通过多次闪光诱导光谱分析，我们发现cyt c-551在第一次闪光和第二次闪光后，半衰期分别为60 μs和100 μs左右。cyt c-551的这些行为可以用两个功能等效的cyt c模型来解释，并且与供体侧的同二聚体模型一致。上述明显不同的速率可以用以下事实来解释：在第一次闪光后，两个cyt c-551可以给电子给P840，而在第二次闪光后，大多数PS-C只有一个电子给电子。当PS-C暴露于空气中时，受体侧发生快速失活，失活的实际位置仍有待研究。从黄貂草中分离到4个2[4Fe-4S]型铁氧化还原蛋白（Fds）。在菠菜PS-C和FNR存在的情况下，它们都支持NADP^+的有效还原。据报道，来自绿硫细菌的Fds对氧气极其敏感。然而，这些Fds对氧气相对不敏感，在4℃的好氧条件下保存，其失活率仅为10-15%。我们从移动Heliobacillus mobilis中纯化了两个Fds。其中一种对氧极为敏感，而另一种对氧相对不敏感。