Department of Chemistry and Molecular Biology, University of Gothenburg, SE-40530 Gothenburg, Sweden; email:
Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich, 8093 Zürich, Switzerland.
Annu Rev Biochem. 2019 Jun 20;88:59-83. doi: 10.1146/annurev-biochem-013118-111327. Epub 2019 Apr 3.
Directional transport of protons across an energy transducing membrane-proton pumping-is ubiquitous in biology. Bacteriorhodopsin (bR) is a light-driven proton pump that is activated by a buried all- retinal chromophore being photoisomerized to a 13- conformation. The mechanism by which photoisomerization initiates directional proton transport against a proton concentration gradient has been studied by a myriad of biochemical, biophysical, and structural techniques. X-ray free electron lasers (XFELs) have created new opportunities to probe the structural dynamics of bR at room temperature on timescales from femtoseconds to milliseconds using time-resolved serial femtosecond crystallography (TR-SFX). Wereview these recent developments and highlight where XFEL studies reveal new details concerning the structural mechanism of retinal photoisomerization and proton pumping. We also discuss the extent to which these insights were anticipated by earlier intermediate trapping studies using synchrotron radiation. TR-SFX will open up the field for dynamical studies of other proteins that are not naturally light-sensitive.
质子在能量转换膜中的定向转运——质子泵——在生物学中无处不在。细菌视紫红质（bR）是一种光驱动的质子泵，它通过被掩埋的全视黄醛发色团的光异构化来激活，形成 13-构象。光异构化如何引发与质子浓度梯度相反的定向质子转运的机制已通过多种生化、生物物理和结构技术进行了研究。X 射线自由电子激光（XFEL）为使用飞秒到毫秒时间尺度的时间分辨连续飞秒晶体学（TR-SFX）在室温下探测 bR 的结构动力学提供了新的机会。我们回顾了这些最新的发展，并强调了 XFEL 研究揭示了关于视黄醛光异构化和质子泵的结构机制的哪些新细节。我们还讨论了这些见解在多大程度上可以通过使用同步辐射的早期中间捕获研究来预测。TR-SFX 将为其他非天然光敏感蛋白的动力学研究开辟领域。
