Bustamante P L, Loach P A
Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500.
Biochemistry. 1994 Nov 15;33(45):13329-39. doi: 10.1021/bi00249a020.
The B820 subunit form of the core light-harvesting complex LHI, isolated from the photosynthetic bacterium Rhodospirillum rubrum, was combined in a reassociation assay with the reaction center (RC) isolated from the same or related bacteria. This reassociation produced a photoreceptor complex (PRC) which appeared, by absorption spectroscopy, circular dichroism measurements, and kinetic absorption spectroscopy measuring transient photochanges, as analogous to the PRC in the intact bacteria. Energy transfer between the LHI and reaction center progressed with almost 100% efficiency and indicated a cooperative pattern of transfer. Treatment of the RC with proteinase K resulted in peptide cleavages of all three polypeptides of the RC but did not alter the light-induced charge separation in the RC or prevent the reassociation of the LHI and modified RC. Energy transfer efficiency from LHI to RC still approached 100% but the cooperative behavior seen in reconstitutions with the intact RC was not observed. Initial experiments using interspecies reassociations (LHI from Rhodobacter sphaeroides and RC from Rs. rubrum) showed a low efficiency of energy transfer from LHI to RC. Possible association domains for the LHI-RC interaction based on considerations of the comparative amino acid sequences of the RC of each bacteria and the most feasible remaining residues in the proteinase K treated RC are considered.
从光合细菌红螺菌（Rhodospirillum rubrum）中分离得到的核心捕光复合物LHI的B820亚基形式，在重缔合试验中与从相同或相关细菌中分离得到的反应中心（RC）相结合。这种重缔合产生了一种光感受器复合物（PRC），通过吸收光谱、圆二色性测量以及测量瞬态光变化的动力学吸收光谱表明，它类似于完整细菌中的PRC。LHI和反应中心之间的能量转移效率几乎达到100%，并显示出协同转移模式。用蛋白酶K处理RC会导致RC的所有三种多肽发生肽段切割，但不会改变RC中的光诱导电荷分离，也不会阻止LHI与修饰后的RC重缔合。从LHI到RC的能量转移效率仍接近100%，但在与完整RC的重组中所观察到的协同行为未出现。最初使用种间重缔合（来自球形红杆菌（Rhodobacter sphaeroides）的LHI和来自红螺菌的RC）的实验表明，从LHI到RC的能量转移效率较低。基于对每种细菌RC的比较氨基酸序列以及蛋白酶K处理后的RC中最可能残留的残基的考虑，探讨了LHI - RC相互作用的可能结合结构域。
