Elghobashi-Meinhardt Nadia, Phatak Prasad, Bondar Ana-Nicoleta, Elstner Marcus, Smith Jeremy C
Department of Physical and Theoretical Chemistry, Theoretical Molecular Biophysics, Institute for Chemistry und Biochemistry, Freie Universität Berlin, Fabeckstr. 36a, Berlin, 14169, Germany.
Institute of Physical and Theoretical Chemistry, TU Braunschweig, 38106, Braunschweig, Germany.
J Membr Biol. 2018 Jun;251(3):315-327. doi: 10.1007/s00232-018-0027-x. Epub 2018 Mar 8.
For the photocycle of the membrane protein bacteriorhodopsin to proceed efficiently, the thermal 13-cis to all-trans back-isomerization of the retinal chromophore must return the protein to its resting state on a time-scale of milliseconds. Here, we report on quantum mechanical/molecular mechanical energy calculations examining the structural and energetic determinants of the retinal cis-trans isomerization in the protein environment. The results suggest that a hydrogen-bonded network consisting of the retinal Schiff base, active site amino acid residues, and water molecules can stabilize the twisted retinal, thus reducing the intrinsic energy cost of the cis-trans thermal isomerization barrier.
为使膜蛋白细菌视紫红质的光循环高效进行，视黄醛发色团从热致13-顺式到全反式的逆向异构化必须在毫秒时间尺度内将蛋白质恢复到其静止状态。在此，我们报告了量子力学/分子力学能量计算，研究了蛋白质环境中视黄醛顺反异构化的结构和能量决定因素。结果表明，由视黄醛席夫碱、活性位点氨基酸残基和水分子组成的氢键网络可以稳定扭曲的视黄醛，从而降低顺反热异构化势垒的内在能量成本。
