Department of Chemistry and Biochemistry, University of California, 405 Hilgard Avenue, Los Angeles, CA 90024.
Proc Natl Acad Sci U S A. 1985 Jun;82(11):3662-4. doi: 10.1073/pnas.82.11.3662.
The transient absorption changes occurring at 297 nm during the photocycles of the deionized and acidified bacteriorhodopsins (blue membranes) were studied. As opposed to what happens during the photocycle of the purple membrane, for the blue membranes only the fast absorption increase corresponding to trans-cis isomerization of the retinal chromophore is present; the slow rise attributed to the tyrosine deprotonation is not observed. The addition of different salts to the deionized membrane restores the original color and causes a tyrosine deprotonation during the photocycle. This suggests that the presence of cations is required for the deprotonation of tyrosine as it is for the deprotonation of the retinylidene Schiff base. These results are discussed in terms of the recently proposed cation model for the observed deprotonation processes in the photocycle of bacteriorhodopsin.
在去离子和酸化的菌紫质(蓝膜)的光循环过程中,研究了在 297nm 处发生的瞬态吸收变化。与紫膜光循环过程中发生的情况相反,对于蓝膜,只有对应于视黄醛发色团的反式-顺式异构化的快速吸收增加是存在的;而没有观察到归因于酪氨酸去质子化的缓慢上升。向去离子膜中添加不同的盐会恢复原始颜色,并在光循环过程中引起酪氨酸去质子化。这表明,阳离子的存在对于酪氨酸的去质子化是必需的,就像对于视黄醛亚胺 Schiff 碱的去质子化一样。这些结果是根据最近提出的阳离子模型来讨论的,该模型用于解释菌紫质光循环中观察到的去质子化过程。