the importance of a native weak hydrogen bond between C218ARII and D92ARII for proper proton translocation in the CP channel during N-decay. A putative role for the D92ARII-C218ARII interhelical hydrogen bond in the function of ARII is discussed.Production of a light-gated proton channel by replacing the retinal chromophore with its synthetic vinylene derivative Takayama, R. Kaneko, A. Okitsu, T. Tsunoda, S. P. Shimono, K. Mizuno, M. Kojima, K. Tsukamoto, T. Kandori, H. Mizutani, Y. Wada, A. Sudo, Y. J. Phys. Chem. Lett., Vol. 9(11),pp.2857-2862201830 DDOI: 10.1021/acs.jpclett.8b00879Rhodopsin is widely distributed in organisms as a membrane-embedded photoreceptor protein, consisting of the apoprotein opsin and vitamin-A aldehyde retinal, A1-retinal and A2-retinal being the natural chromophores. Modifications of opsin (e.g., by mutations) have provided insight into the molecular mechanism of the light-induced functions of rhodopsins as well as providing tools in chemical biology to control cellular activity by light. Instead of the apoprotein opsin, in this study, we focused on the retinal chromophore and synthesized three vinylene derivatives of A2-retinal. One of them, C(14)-vinylene A2-retinal (14V-A2), was successfully incorporated into the opsin of a light-driven proton pump archaerhodopsin-3 (AR3). Electrophysiological experiments revealed that the opsin of AR3 (archaeopsin3, AO3) with 14V-A2 functions as a light-gated proton channel. The engineered proton channel showed characteristic photochemical properties, which are significantly different from those of AR3. Thus, we successfully produced a proton channel by replacing the chromophore of AR3
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