Dipartimento di Chimica, Università di Siena, Siena I-53100, Italy.
Proc Natl Acad Sci U S A. 2010 Dec 14;107(50):21322-6. doi: 10.1073/pnas.1015085107. Epub 2010 Nov 22.
The implementation of multiconfigurational quantum chemistry methods into a quantum-mechanics/molecular-mechanics protocol has allowed the construction of a realistic computer model for the sensory rhodopsin of the cyanobacterium Anabaena PCC 7120. The model, which reproduces the absorption spectra of both the all-trans and 13-cis forms of the protein and their associated K and L intermediates, is employed to investigate the light-driven steps of the photochromic cycle exhibited by the protein. It is found that the photoisomerizations of the all-trans and 13-cis retinal chromophores occur through unidirectional, counterclockwise 180° rotations of the =C14-C15= moiety with respect to the Lys210-linked end of the chromophore axis. Thus, the sequential interconversions of the all-trans and 13-cis forms during a single photochromic cycle yield a complete (360°) unidirectional rotation of the =C14-C15= moiety. This finding implies that Anabaena sensory rhodopsin is a biological realization of a light-driven molecular rotor.
多组态量子化学方法的实现被引入量子力学/分子力学协议中，从而构建了一个现实的计算机模型，用于研究蓝藻鱼腥藻 PCC 7120 的感光视紫红质。该模型再现了蛋白质的全反式和 13-顺式形式及其相关的 K 和 L 中间体的吸收光谱，并被用于研究蛋白质表现出的光致变色循环的光驱动步骤。结果发现，全反式和 13-顺式视黄醛发色团的光致异构化通过相对于发色团轴上与 Lys210 相连的末端的 =C14-C15= 部分进行单向逆时针 180°旋转来发生。因此，在单个光致变色循环中，全反式和 13-顺式形式的连续相互转化导致 =C14-C15= 部分的完全（360°）单向旋转。这一发现表明，鱼腥藻感光视紫红质是光驱动分子转子的生物实现。
