Evidence for two active branches for electron transfer in photosystem I
Evidence for two active branches for electron transfer in photosystem I
复制标题
DOI：
10.1073/pnas.081078898
复制
发表时间：
2001-04-10
影响因子：
11.1
通讯作者：
Redding, K
中科院分区：
文献类型：
--
作者：
Guergova-Kuras, M;Boudreaux, B;Redding, K
所有的光合反应中心都有一个共同的结构主题。两个相关的，完整的膜多肽螯合电子转移辅因子成两个准对称的分支，其中每个都包含一个醌。在II型反应中心[光系统（PS）II和蛋白细菌反应中心]中，电子转移仅沿其中一个分支进行，而另一个分支上的移动的醌用作末端受体。PS I使用铁硫簇作为末端受体，醌仅作为电子转移的中间体。人们一直致力于理解II型反应中心电子传输的单向性，人们普遍认为PS I也具有这一特征。我们已经测试了这个想法，通过研究在体内的电子转移的醌在突变体PS I反应中心的动力学。这种转移与两个动力学组件，我们表明，突变的一个分支中的醌附近的残基特别影响更快的组件，而相应的突变在其他分支特别影响较慢的组件。我们的结论是，两个电子转移分支在PS I是活跃的。
All photosynthetic reaction centers share a common structural theme. Two related, integral membrane polypeptides sequester electron transfer cofactors into two quasi-symmetrical branches, each of which incorporates a quinone. In type II reaction centers [photosystem (PS) II and proteobacterial reaction centers], electron transfer proceeds down only one of the branches, and the mobile quinone on the other branch is used as a terminal acceptor. PS I uses iron-sulfur clusters as terminal acceptors, and the quinone serves only as an intermediary in electron transfer. Much effort has been devoted to understanding the unidirectionality of electron transport in type II reaction centers, and it was widely thought that PS I would share this feature. We have tested this idea by examining in vivo kinetics of electron transfer from the quinone in mutant PS I reaction centers. This transfer is associated with two kinetic components, and we show that mutation of a residue near the quinone in one branch specifically affects the faster component, while the corresponding mutation in the other branch specifically affects the slower component. We conclude that both electron transfer branches in PS I are active.