Wood Kathleen, Lehnert Ursula, Kessler Brigitte, Zaccai Giuseppe, Oesterhelt Dieter
Institut Laue-Langevin, BP 156, F-38042 Grenoble cedex 9, France.
Biophys J. 2008 Jul;95(1):194-202. doi: 10.1529/biophysj.107.120386. Epub 2008 Mar 13.
We used neutron scattering and specific hydrogen-deuterium labeling to investigate the thermal dynamics of isotope-labeled amino acids and retinal, predominantly in the active core and extracellular moiety of bacteriorhodopsin (BR) in the purple membrane and the dynamical response to hydration. Measurements on two neutron spectrometers allowed two populations of motions to be characterized. The lower amplitude motions were found to be the same for both the labeled amino acids and retinal of BR and the global membrane. The larger amplitude dynamics of the labeled part, however, were found to be more resilient than the average membrane, suggesting their functional importance. The response to hydration was characterized, showing that the labeled part of BR is not shielded from hydration effects. The results suggest that the inhibition of high-amplitude motions by lowering hydration may play a key role in the slowing down of the photocycle and the proton pumping activity of BR.
我们使用中子散射和特定的氢-氘标记来研究同位素标记的氨基酸和视黄醛的热动力学，主要针对紫色膜中细菌视紫红质（BR）的活性核心和细胞外部分以及对水合作用的动态响应。在两台中子光谱仪上进行的测量使得能够表征两种运动群体。结果发现，对于BR的标记氨基酸和视黄醛以及整体膜而言，较低幅度的运动是相同的。然而，标记部分的较大幅度动力学被发现比平均膜更具弹性，这表明它们在功能上具有重要性。对水合作用的响应得到了表征，结果表明BR的标记部分并未免受水合作用的影响。这些结果表明，通过降低水合作用来抑制高幅度运动可能在减缓BR的光循环和质子泵浦活性中起关键作用。
