Biophysical Chemistry on photobrhodopsin, a sensor for a negative taxis of Halobacterium

pharaonis phoborhodopsin（ppR）是一种负趋光性感受器。光照激发ppR，其弛豫到ppR的原始基态。这种线性和循环的光化学过程称为光循环。在细胞膜内，ppR与转换蛋白pHtrII形成复合物，该复合物将光信号传输到细胞质。通过高压实验和SVD分析，发现了一种新的光致中间体。(2)在光循环过程中释放质子的氨基酸残基的归属。(3)配合物化学计量的确定（4）配合物形成所必需的氨基酸残基的归属。(5)在光循环过程中，复合物的KD值变化了100倍。(6)螺旋-螺旋相互作用对颜色调节的重要性。

pharaonis phoborhodopsin (ppR) is a sensor for negative phototaxis of Natronobacterium pharaonis. Illumination excites ppR, which relaxed to the original ground state of ppR. This linear and cyclic photochemistry is called photocycle. Within membranes, ppR forms a complex with a transducer protein, pHtrII, and this complex transmits photo-signals to cytoplasm. This research clarified as follows(1) Discovery of a new photo-intermediate after high-pressure experiments and SVD analysis.(2) Assignment of an amino acid residue from which proton is released during photocycling.(3) Determination of the stoichiometry of the complex(4) Assignment of essential amino acid residues for the formation of the complex.(5) One hundred-fold alternation of KD values of the complex during photocycling.(6) Importance of helix-helix interaction for the color tuning.