Pico G A, Houssier C
Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario, (Argentina, Belgium.
Biochim Biophys Acta. 1989 Nov 30;999(2):128-34. doi: 10.1016/0167-4838(89)90209-4.
The binding of hydroxyl and keto bile salts to bovine serum albumin was studied by fluorescence and circular dichroism spectroscopies. It was found that the hydroxyl and keto bile salts produced a quenching of the native fluorescence emission of the protein at 350 nm. In the ligand-protein saturation conditions, cholanate-3-one, cholanate-3,6-dione and beta 5-cholanate produced a 100% fluorescence quenching, while hydroxy bile salts produced only a 50% quenching. This demonstrates that the two tryptophan residues of the protein are accessible to the keto bile salts, while only one tryptophan residue is accessible to the hydroxy parent compounds. Keto bile salts produced a change in the circular is related to a microrearrangement of the environment at the albumin-binding sites. All the tested bile salts produced quenching of the fluorescence probe, 1-aniline-8-naphthalene sulfonate, which is not covalently bound to the protein. This effect is due to an energy transfer between the tryptophan residues and the acceptor fluorescence probe. The binding of hydroxyl bile salts was associated with an endothermic process, while keto bile salts-albumin interaction was associated with a negative enthalpic change.
通过荧光光谱法和圆二色光谱法研究了羟基胆盐和酮胆盐与牛血清白蛋白的结合情况。结果发现，羟基胆盐和酮胆盐会使蛋白质在350nm处的天然荧光发射发生猝灭。在配体 - 蛋白质饱和条件下，胆烷酸 - 3 - 酮、胆烷酸 - 3,6 - 二酮和β5 - 胆烷酸会导致100%的荧光猝灭，而羟基胆盐仅导致50%的猝灭。这表明蛋白质的两个色氨酸残基可被酮胆盐接近，而羟基母体化合物只能接近一个色氨酸残基。酮胆盐使圆二色性发生变化，这与白蛋白结合位点处环境的微重排有关。所有测试的胆盐都会使荧光探针1 - 苯胺 - 8 - 萘磺酸盐（未与蛋白质共价结合）的荧光猝灭。这种效应是由于色氨酸残基与受体荧光探针之间的能量转移。羟基胆盐的结合与吸热过程相关，而酮胆盐 - 白蛋白相互作用与负的焓变相关。
