Investigation into the source of electron transfer asymmetry in bacterial reaction centers.
Investigation into the source of electron transfer asymmetry in bacterial reaction centers.
复制标题
细菌反应中心电子转移不对称来源的调查。
DOI：
10.1021/bi00098a006
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发表时间：
1991
期刊：
影响因子：
2.9
通讯作者：
Schenck,CC
中科院分区：
文献类型：
--
作者：
McDowell,LM;Gaul,D;Kirmaier,C;Holten,D;Schenck,CC
摘要：我们研究了球形红杆菌两个对称性相关突变体(His-L173和His-M202)中与二聚体初级电子供体(His-L173和His-M202)的中心镁离子相关的组氨酸残基转变为亮氨酸的初级光化学，得到了细菌叶绿素(BCHL)/细菌叶绿素(BPH)异二聚体。两个突变体(L)H173L和(M)H202L的反应中心具有非常相似的光谱和动力学性质，尽管它们与野生型反应中心有很大的不同。在这两个突变体中，正如野生型RCS一样，观察到电子转移到BPhL而不是BPhM。这些结果表明，在野生型RCS中激发的BCHL二聚体(P*)的电荷分布的不对称性(由于两个相对的传统分子内电荷转移态的不同贡献)对电子转移的方向性只有轻微的贡献。结果还表明，P的两个BChl与L和M多肽上的生色团的差异轨道重叠对BPhL的优先电子转移没有实质性的贡献。
Revised Manuscript Received June 3, 1991 abstract: We have investigated the primary photochemistry of two symmetry-related mutants of Rhodobacter sphaeroides in which the histidine residues associated with the central Mg2+ ions of the two bacteriochlorophylls of the dimericprimary electron donor (His-L173 and His-M202) have been changed to leucine, affording bacteriochlorophyll (BChl)/bacteriopheophytin (BPh) heterodimers. Reaction centers (RCs) from thetwo mutants,(L) H173L and (M) H202L, have remarkably similar spectraland kinetic properties, although they are quite different from those of wild-type RCs. In both mutants, as in wild-type RCs, electron transfer to BPhL and not to BPhM is observed. These results suggest that asymmetry in the charge distribution of the excited BChl dimer (P*) in wild-type RCs (due to differing contributions of the two opposing intradimer charge-transfer states) contributes only modestly to the directionality of electron transfer. The resultsalso suggest that differential orbital overlap of the two BChls of P with the chromophores on the L and M polypeptides does not contribute substantially to preferential electron transfer to BPhL.