CONTROL OF ELECTRON-TRANSFER BETWEEN THE L-SIDE AND M-SIDE OF PHOTOSYNTHETIC REACTION CENTERS
CONTROL OF ELECTRON-TRANSFER BETWEEN THE L-SIDE AND M-SIDE OF PHOTOSYNTHETIC REACTION CENTERS
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DOI：
10.1126/science.7638616
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发表时间：
1995-08-18
期刊：
影响因子：
56.9
通讯作者：
KIRMAIER, C
中科院分区：
文献类型：
--
作者：
HELLER, BA;HOLTEN, D;KIRMAIER, C
在一个荚膜红杆菌突变体的光合反应中心的L侧辅助细菌叶绿素（BChl(L)）的V环附近引入了一个天冬氨酸残基，其中一个His也取代了m多肽上的Leu 212。在G(M201)D/L(M212)H双突变体中，电荷分离的初始阶段产生了类似于70%的电子转移到L侧辅因子，类似于15%的快速失活到基态，类似于15%的电子转移到所谓的失活M侧细菌叶绿素（BPh(M)）。本文认为，在M201处引入的Asp调节了BChl(L)的还原电位，从而改变了电荷分离的能量学。结果表明，单个氨基酸残基可以通过其对电荷分离态自由能的影响，有效地决定RC l侧正向电子转移反应、电荷重组过程和电子向m侧发色团转移之间的平衡。
An aspartic acid residue has been introduced near ring V of the L-side accessory bacteriochlorophyll (BChl(L)) of the photosynthetic reaction center in a Rhodobacter capsulatus mutant in which a His also replaces Leu 212 on the M-polypeptide. The initial stage of charge separation in the G(M201)D/L(M212)H double mutant yields similar to 70 percent electron transfer to the L-side cofactors, similar to 15 percent rapid deactivation to the ground state, and similar to 15 percent electron transfer to the so-called inactive M-side bacteriopheophytin (BPh(M)). It is suggested here that the Asp introduced at M201 modulates the reduction potential of BChl(L), thereby changing the energetics of charge separation. The results demonstrate that an individual amino acid residue can, through its influence on the free energies of the charge-separated states, effectively dictate the balance between the forward electron transfer reactions on the L-side of the RC, the charge-recombination processes, and electron transfer to the M-side chromophores.