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首页> 外文期刊>Biochemistry >Chromophore-protein-water interactions in the L intermediate of bacteriorhodopsin: FTIR study of the photoreaction of L at 80 K.
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Chromophore-protein-water interactions in the L intermediate of bacteriorhodopsin: FTIR study of the photoreaction of L at 80 K.

机译：细菌视紫红质L中间体中的发色团-蛋白质-水相互作用：FTIR研究L在80 K下的光反应。

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摘要

Using FTIR spectroscopy, perturbations of several residues and internal water molecules have been detected when light transforms all-trans bacteriorhodopsin (BR) to its L intermediate having a 13-cis chromophore. Illumination of L at 80 K results in an intermediate L' absorbing around 550 nm. L' thermally converts to the original BR only at >130 K. In this study, we used the light-induced transformation of L to L' at 80 K to identify some amino acid residues and water molecules that closely interact with the chromophore and distinguish them from those residues not affected by the photoreaction. The L minus L' FTIR difference spectrum shows that the chromophore in L' is in the all-trans configuration. The perturbed states of Asp96 and Val49 and of the environment along the aliphatic part of the retinal and Lys216 seen in L are not affected by the L --> L' photoreaction. On the other hand, the environments of the Schiff base of the chromophore, of Asp115, and of water molecules close to Asp85 returned in L' to their state in which they originally had existed in BR. The water molecules that are affected by the mutations of Thr46 and Asp96 also change to a different state in the L --> L' transition, as indicated by transformation of a water O-H vibrational band at 3497 cm-1 in L into an intense peak at 3549 cm-1 in L'. Notably, this change of water bands in the L --> L' transition at 80 K is entirely different from the changes observed in the BR --> K photoreaction at the same temperature, which does not show such intense bands. These results suggest that these water molecules move closer to the Schiff base as a hydrogen bonding cluster in L and L', presumably to stabilize its protonated state during the BR to L transition. They may contribute to the structural constraints that prevent L from returning to the initial BR upon illumination at 80 K.
机译：使用FTIR光谱学，当光将全反细菌视紫红质（BR）转变为其具有13个顺式生色团的L中间体时，已经检测到一些残留物和内部水分子的扰动。 L在80 K的照度导致中间L'吸收约550 nm。 L'仅在> 130 K时才热转化为原始BR。在这项研究中，我们使用光诱导的L在80 K时向L'的转化，以识别与发色团紧密相互作用并区分的一些氨基酸残基和水分子它们来自不受光反应影响的那些残留物。 L减去L'的FTIR差异光谱表明，L'中的发色团处于全反式构型。 L中看到的Asp96和Val49以及视网膜脂族部分和Lys216沿周围环境的扰动状态不受L-> L'光反应的影响。另一方面，发色团的席夫碱，Asp115以及接近Asp85的水分子的环境以L'的状态返回到它们最初存在于BR中的状态。受Thr46和Asp96突变影响的水分子在L-> L'跃迁中也变为不同状态，如L中3497 cm-1处的水OH振动带转变为强峰所表明在L'中的3549 cm-1处。值得注意的是，在80 K时L-> L'跃迁中水带的这种变化与在相同温度下BR-> K光反应中观察到的变化完全不同，后者没有显示出如此强的带。这些结果表明，这些水分子在L和L'中作为氢键簇更靠近席夫碱，大概是在BR向L跃迁期间稳定其质子化状态。它们可能会导致结构上的限制，从而阻止L在80 K光照下返回初始BR。

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