Stowell M H, McPhillips T M, Rees D C, Soltis S M, Abresch E, Feher G
Division of Chemistry and Chemical Engineering, 147-75CH, California Institute of Technology, Pasadena, CA 91125, USA.
Science. 1997 May 2;276(5313):812-6. doi: 10.1126/science.276.5313.812.
High resolution x-ray diffraction data from crystals of the Rhodobacter sphaeroides photosynthetic reaction center (RC) have been collected at cryogenic temperature in the dark and under illumination, and the structures were refined at 2.2 and 2.6 angstrom resolution, respectively. In the charge-separated D+QAQB- state (where D is the primary electron donor (a bacteriochlorophyll dimer), and QA and QB are the primary and secondary quinone acceptors, respectively), QB- is located approximately 5 angstroms from the QB position in the charge-neutral (DQAQB) state, and has undergone a 180 degrees propeller twist around the isoprene chain. A model based on the difference between the two structures is proposed to explain the observed kinetics of electron transfer from QA-QB to QAQB- and the relative binding affinities of the different ubiquinone species in the QB pocket. In addition, several water channels (putative proton pathways) leading from the QB pocket to the surface of the RC were delineated, one of which leads directly to the membrane surface.
来自球形红细菌光合反应中心（RC）晶体的高分辨率X射线衍射数据已在低温下于黑暗和光照条件下收集，并且结构分别在2.2埃和2.6埃分辨率下进行了精修。在电荷分离的D⁺QAQB⁻状态（其中D是初级电子供体（细菌叶绿素二聚体），QA和QB分别是初级和次级醌受体）中，QB⁻位于电荷中性（DQAQB）状态下QB位置约5埃处，并且围绕异戊二烯链发生了180度的螺旋扭曲。基于两种结构之间差异的模型被提出来解释观察到的从QA⁻QB到QAQB⁻的电子转移动力学以及不同泛醌物种在QB口袋中的相对结合亲和力。此外，描绘了几条从QB口袋通向RC表面的水通道（假定的质子途径），其中一条直接通向膜表面。
