Jacobsen J, Brodersen R
J Biol Chem. 1983 May 25;258(10):6319-26.
After binding of bilirubin to human serum albumin (1:1), a train of relaxational changes of conformation takes place. The late part of these processes, occurring in the time interval 1-500 s, has been studied by recording the changes of light absorption. Similar processes have been demonstrated after binding of fatty acid anion to the bilirubin-albumin complex as well as after a pH-jump from 6 to 9. Solvent perturbation spectra obtained on the addition of 20% sucrose have failed to demonstrate exposure of the bilirubin chromophores in the complex to the surrounding medium. Xanthobilirubinate which has a single dipyrrolic chromophore compared to the two of bilirubin is bound to albumin in competition with bilirubin, as concluded from co-binding studies with monoacetyldiaminodiphenylsulfone and diazepam, probing two different binding functions of the albumin molecule. Late conformational changes were absent after binding of xanthobilirubinate. Binding of fatty acid to the complex and a pH-jump did not affect the spectrum of xanthobilirubinate-human serum albumin. The findings can be explained by a model, previously proposed, in which the late spectral changes are affected by rotation of one half-domain of albumin, binding one bilirubin chromophore, relative to another half-domain to which the second bilirubin chromophore is bound, whereby a change of exiton splitting occurs. Such changes are not seen with the complex of xanthobilirubinate and albumin, since only a single chromophore is present.
胆红素与人类血清白蛋白以1:1结合后，会发生一系列构象松弛变化。这些过程的后期，即发生在1 - 500秒时间间隔内的部分，已通过记录光吸收变化进行了研究。脂肪酸阴离子与胆红素 - 白蛋白复合物结合后，以及pH从6跃升至9后，也观察到了类似的过程。添加20%蔗糖后获得的溶剂扰动光谱未能证明复合物中胆红素发色团暴露于周围介质中。与胆红素的两个双吡咯发色团相比，具有单个双吡咯发色团的黄胆胆红素与白蛋白结合时会与胆红素竞争，这是通过与单乙酰二氨基二苯砜和地西泮的共结合研究得出的结论，该研究探测了白蛋白分子的两种不同结合功能。黄胆胆红素结合后不存在后期构象变化。脂肪酸与复合物的结合以及pH跃变不会影响黄胆胆红素 - 人类血清白蛋白的光谱。这些发现可以用先前提出的一个模型来解释，在该模型中，后期光谱变化受白蛋白一个半结构域的旋转影响，该半结构域结合一个胆红素发色团，相对于结合第二个胆红素发色团的另一个半结构域，从而发生激子分裂的变化。黄胆胆红素与白蛋白的复合物未观察到此类变化，因为只存在单个发色团。
