Primary light-energy conversion in tetrameric chlorophyll structure of photosystem II and bacterial reaction centers: I. A review-猫眼课题宝

光系统II四聚体叶绿素结构和细菌反应中心的初级光能转换：一、综述

DOI：

发表时间：

2008

期刊：

Photosynthesis Research

影响因子：

3.7

通讯作者：

中科院分区：

生物学3区

文献类型：

作者：

R. A. Khatypov;A. Khmelnitskiy;M. M. Leonova;L. Vasilieva;V. Shuvalov

综述了绿色植物光系统II（PSII）反应中心和细菌反应中心（BRC）中的四聚体叶绿素（（B）Chl）结构的相似性及其在初级电荷分离中的重要作用。对PSII反应中心的斯塔克效应测量已经揭示了在~730 nm处跃迁的增加的偶极矩（Frese等人，Biochemistry 42：9205 - 9213，2003）。发现（Heber和Shuvalov，Photosynth Res 84：84 - 91，2005）在不同的生物体中观察到685和720 nm处的两个荧光带。这两种形式记录在QA光还原作用光谱中。在低温下PSII的核心复合物中也获得了类似的结果（Hughes等人，Biochim Biophys Acta 1757：841 - 851，2006）。在所有情况下，远红外吸收和发射可以解释为具有电荷转移特征的状态的指示，其中叶绿素单体起电子供体的作用。细菌叶绿素单体（BA和BB）在BRC中的作用可以通过Mg中心原子轴向配体的不同突变来揭示。组氨酸L153被酪氨酸或亮氨酸取代以及组氨酸M182被亮氨酸取代（双突变体）的RC在分离状态下不稳定。它们在无天线膜中通过不同种类的光谱学进行了研究，包括具有飞秒时间分辨率的光谱学。结果发现，单一突变（L153 HY）是伴随着BA分子吸收消失，近802 nm和由14倍的光化学活性降低测量与ms的时间分辨率。P870 * 的寿命增加到约200 ps，与非常低的电子转移到A-分支的速率一致。在双突变体L153 HY + M182 HL中，BA似乎丢失，BB被细菌脱镁叶绿素Φ B取代，在800 nm附近没有任何吸收。飞秒测量揭示了电子转移到B-分支的时间常数为~2 ps。这些结果进行了讨论的强制性作用的BA和Φ B分子位于P附近的有效的电子转移从P *。

The purpose of the review is to show that the tetrameric (bacterio)chlorophyll ((B)Chl) structures in reaction centers of photosystem II (PSII) of green plants and in bacterial reaction centers (BRCs) are similar and play a key role in the primary charge separation. The Stark effect measurements on PSII reaction centers have revealed an increased dipole moment for the transition at ~730 nm (Frese et al., Biochemistry 42:9205–9213, 2003). It was found (Heber and Shuvalov, Photosynth Res 84:84–91, 2005) that two fluorescent bands at 685 and 720 nm are observed in different organisms. These two forms are registered in the action spectrum of QA photoreduction. Similar results were obtained in core complexes of PSII at low temperature (Hughes et al., Biochim Biophys Acta 1757: 841–851, 2006). In all cases the far-red absorption and emission can be interpreted as indication of the state with charge transfer character in which the chlorophyll monomer plays a role of an electron donor. The role of bacteriochlorophyll monomers (BA and BB) in BRCs can be revealed by different mutations of axial ligand for Mg central atoms. RCs with substitution of histidine L153 by tyrosine or leucine and of histidine M182 by leucine (double mutant) are not stable in isolated state. They were studied in antennaless membrane by different kinds of spectroscopy including one with femtosecond time resolution. It was found that the single mutation (L153HY) was accompanied by disappearance of BA molecule absorption near 802 nm and by 14-fold decrease of photochemical activity measured with ms time resolution. The lifetime of P870* increased up to ~200 ps in agreement with very low rate of the electron transfer to A-branch. In the double mutant L153HY + M182HL, the BA appears to be lost and BB is replaced by bacteriopheophytin ΦB with the absence of any absorption near 800 nm. Femtosecond measurements have revealed the electron transfer to B-branch with a time constant of ~2 ps. These results are discussed in terms of obligatory role of BA and ΦB molecules located near P for efficient electron transfer from P*.