Bayley H, Radhakrishnan R, Huang K S, Khorana H G
J Biol Chem. 1981 Apr 25;256(8):3797-801.
The properties of bacteriorhodopsin in which the natural cofactor, retinal (Fig. 1, I), has been replaced by the synthetic analog, phenyl retinal (Fig. 1, II), have been studied. Phenyl retinal binds at the same site as retinal and supports light-dependent transmembrane proton translocation in phospholipid vesicles that contain bacterio-opsin. This result allows us to rule out proton abstraction from the beta-ionone ring of retinal as a step in the catalytic cycle. Furthermore, phenyl retinal, a planar molecule, binds to the apomembrane more rapidly than retinal, which suggests that the rate-determining step in the binding of retinal itself may be the attainment of a planar molecular configuration. The new chromophore undergoes a pH-dependent spectral shift that is not observed in the native membrane.
已经对细菌视紫红质的性质进行了研究，其中天然辅因子视黄醛（图1，I）已被合成类似物苯基视黄醛（图1，II）所取代。苯基视黄醛与视黄醛结合在相同位点，并在含有细菌视蛋白的磷脂囊泡中支持光依赖性跨膜质子转运。这一结果使我们能够排除在催化循环中从视黄醛的β-紫罗兰酮环提取质子这一步骤。此外，苯基视黄醛是一种平面分子，它与脱辅基膜的结合比视黄醛更快，这表明视黄醛自身结合的速率决定步骤可能是达到平面分子构型。这种新的发色团会发生pH依赖性光谱位移，而在天然膜中未观察到这种现象。
