Heyn M P, Borucki B, Otto H
Biophysics Group, Department of Physics, Freie Universität Berlin, Arnimallee 14, D-14195, Berlin, Germany.
Biochim Biophys Acta. 2000 Aug 30;1460(1):60-74. doi: 10.1016/s0005-2728(00)00130-4.
Light-induced isomerization leads to orientational changes of the retinylidene chromophore of bacteriorhodopsin in its binding pocket. The chromophore reorientation has been characterized by the following methods: polarized absorption spectroscopy in the visible, UV and IR; polarized resonance Raman scattering; solid-state deuterium nuclear magnetic resonance; neutron and X-ray diffraction. Most of these experiments were performed at low temperatures with bacteriorhodopsin trapped in one or a mixture of intermediates. Time-resolved measurements at room temperature with bacteriorhodopsin in aqueous suspension can currently only be carried out with transient polarized absorption spectroscopy in the visible. The results obtained to date for the initial state and the K, L and M intermediates are presented and discussed. The most extensive data are available for the M intermediate, which plays an essential role in the function of bacteriorhodopsin. For this intermediate the various methods lead to a consistent picture: the curved all-trans polyene chain in the initial state straightens out in the M intermediate (13-cis) and the chain segment between C(5) and C(13) tilts upwards in the direction of the cytoplasmic surface. The kink at C(13) allows the positions of beta-ionone ring and Schiff base nitrogen to remain approximately fixed.
光诱导异构化导致细菌视紫红质的视黄醛发色团在其结合口袋中发生取向变化。发色团的重新取向已通过以下方法进行了表征：可见光、紫外光和红外光下的偏振吸收光谱；偏振共振拉曼散射；固态氘核磁共振；中子和X射线衍射。这些实验大多在低温下进行，细菌视紫红质被困在一种或多种中间体中。目前，对于水悬浮液中的细菌视紫红质，只能在室温下通过可见光瞬态偏振吸收光谱进行时间分辨测量。本文展示并讨论了迄今为止关于初始状态以及K、L和M中间体所获得的结果。关于M中间体的数据最为丰富，它在细菌视紫红质的功能中起着至关重要的作用。对于这个中间体，各种方法得出了一致的结果：初始状态下弯曲的全反式多烯链在M中间体（13-顺式）中伸直，并且C(5)和C(13)之间的链段朝着细胞质表面向上倾斜。C(13)处的扭结使β-紫罗兰酮环和席夫碱氮的位置大致保持固定。
