Where is the pump switch of bacteriorhodopsin located?

本研究旨在揭示细菌视紫红质(BR)中质子泵的机制。为此，我们应用了低温偏振傅里叶变换红外光谱(FTIR)。BR及其相关蛋白质的高精度FTIR光谱研究结果如下：(1)基于低温FTIR光谱对BR中水分子结构的详细分析，提出了一种新的初级质子转移反应模型。这种方法导致了所谓的“水合开关模型”。根据该模型，质子转移反应受控于水分子从Asp85到Asp212的水合开关。(2)利用同位素标记和突变蛋白，我们鉴定了质子化的Schiff碱和Arg82的伸缩振动，它们都构成了BR中的氢键网络。(3)研究了光驱动氯离子泵卤光紫质中的氢键网络。我们发现氯离子被内部水分子水合的方式不同于BR。(4)傅立叶变换红外光谱分析检测到隐色紫质与其转导蛋白形成了复合体。(5)研究了脉孢子虫视紫红质和视视紫质的蛋白质结构变化。揭示了独特的氢键结构。

This research project aims at revealing the mechanism of proton pump in bacteriorhodopsin(BR). For this aim, we applied low-temperature polarized Fourier-transform infrared(FTIR) spectroscopy. Highly accurate FTIR spectroscopy of BR and related proteins provided the following results.(1)A new model for the primary proton transfer reaction is proposed based on the detailed structural analysis of internal water molecules in BR by low-temperature FTIR spectroscopy. This method led to the so called "hydration switch model". According to the model, the proton transfer reaction is controlled by a hydration switch of a water molecule from Asp85 to Asp212.(2)By use of isotope label and mutant proteins, we identified stretching vibrations of the protonated Schiff base and Arg82,both of which constitute hydrogen-bonding network in BR.(3)Hydrogen-bonding network in halorhodopsin, a light-driven chloride ion pump, is studied. We found that a chloride ion is hydrated by internal water molecules differently from those in BR.(4)Complex formation between pharaonis phoborhodopsin and its transducer protein was detected by FTIR spectroscopy.(5)Protein structural changes of Neurospora rhodopsin and visual rhodopsin were studied. Unique hydrogen-bonding structures are revealed.