Casadio R, Gutowitz H, Mowery P, Taylor M, Stoeckenius W
Biochim Biophys Acta. 1980 Mar 7;590(1):13-23. doi: 10.1016/0005-2728(80)90142-5.
Solubilization of purple membrane with Triton X-100 yields Triton micelles containing bacteriorhodopsin monomers. The absorption maximum of dark-adapted solubilized bacteriorhodopsin is blue-shifted to 549 nm. Light adaption increases the absorbance by 4% and shifts the absorption maximum to 553 nm, i.e., the extent of light adaptation is considerably less than in intact purple membrane. Extraction of dark-adapted bacteriorhodopsin in Triton yields a 13-cis- to all-trans-retinal ratio of 58 : 42 which changes after light adaptation to 38 : 62. It has been shown by Sperling et al. (Sperling, W., Carl, P., Rafferty, Ch.N. and Dencher, N.A. (1977) Biophys. Struct. Mech. 3, 79-94) that light adaptation in intact purple membrane occurs through a branching of the 13-cis photoreaction cycle, so that part of the pigment during each cycle crosses over into the all-trans photoreaction cycle. We explain the decreased extent of light adaptation in solubilized bacteriorhodopsin by assuming a significant back reaction from the all-trans to the 13-cis cycle. This assumption predicts a wavelength dependence of the extent of light adaptation, which is born out by experiment.
用Triton X-100溶解紫膜可得到含有细菌视紫红质单体的Triton胶束。暗适应的溶解态细菌视紫红质的最大吸收峰蓝移至549nm。光适应使吸光度增加4%，最大吸收峰移至553nm，即光适应程度远小于完整紫膜中的情况。在Triton中提取暗适应的细菌视紫红质，其13-顺式视黄醛与全反式视黄醛的比例为58:42，光适应后变为38:62。Sperling等人（Sperling, W., Carl, P., Rafferty, Ch.N.和Dencher, N.A. (1977) Biophys. Struct. Mech. 3, 79 - 94）已经表明，完整紫膜中的光适应是通过13-顺式光反应循环的分支发生的，因此在每个循环中，部分色素会进入全反式光反应循环。我们通过假设从全反式循环到13-顺式循环存在显著的逆向反应来解释溶解态细菌视紫红质中光适应程度降低的现象。这一假设预测了光适应程度的波长依赖性，实验结果证实了这一点。
