Váró G, Zimányi L, Chang M, Ni B, Needleman R, Lanyi J K
Biological Research Center, Hungarian Academy of Sciences, Szeged.
Biophys J. 1992 Mar;61(3):820-6. doi: 10.1016/S0006-3495(92)81887-8.
The switch in the bacteriorhodopsin photocycle, which reorients access of the retinal Schiff base from the extracellular to the cytoplasmic side, was suggested to be an M1----M2 reaction (Váró and Lanyi. 1991. Biochemistry. 30:5008-5015, 5016-5022). Thus, in this light-driven proton pump it is the interconversion of proposed M substates that gives direction to the transport. We find that in monomeric, although not purple membrane-lattice immobilized, D115N bacteriorhodopsin, the absorption maximum of M changes during the photocycle: in the time domain between its rise and decay it shifts 15 nm to the blue relative to the spectrum at earlier times. This large shift strongly supports the existence of two M substates. Since D115 is located near the beta-ionone ring of the retinal, the result raises questions about the possible involvement of the retinal chain or protein residues as far away as 10 A from the Schiff base in the mechanism of the switching reaction.
细菌视紫红质光循环中的转换，即视黄醛席夫碱从细胞外侧重新定向到细胞质侧，被认为是一种M1----M2反应（瓦罗和兰伊。1991年。生物化学。30:5008 - 5015，5016 - 5022）。因此，在这种光驱动质子泵中，正是所提出的M亚态的相互转换为转运提供了方向。我们发现，在单体的D115N细菌视紫红质中，尽管不是固定在紫膜晶格中的，M的最大吸收在光循环过程中发生变化：在其上升和衰减之间的时域内，相对于早期的光谱，它向蓝光方向移动了15纳米。这种大的移动有力地支持了两种M亚态的存在。由于D115位于视黄醛的β-紫罗兰酮环附近，这一结果引发了关于视黄醛链或距离席夫碱达10埃之远的蛋白质残基在转换反应机制中可能参与情况的疑问。
