Trynda L, Przywarska-Boniecka H, Kościukiewicz T
Institute of Chemistry, University of Wrocław, Poland.
J Inorg Biochem. 1990 Feb;38(2):153-67. doi: 10.1016/0162-0134(90)84023-i.
The interaction of bilirubin with aspirin-modified human serum albumin (HSA) and the influence of iron tetrasulfonated phthalocyanine on bilirubin binding by the native protein has been studied by difference spectroscopy and circular dichroism measurements. Spectroscopic studies of the systems containing bilirubin and aspirin-modified HSA compared to the analogous systems with the native protein have shown that selective acetylation of albumin at lysine 199 inhibits bilirubin binding by this protein. In both cases, interaction between bilirubin and albumin leads to complex formation at a molar ratio of ligand to protein of 2:1. The studies of the reaction of bilirubin with fragments of albumin produced by reaction with CNBr have demonstrated that one of the strong bilirubin binding sites is located in the M fragment and is close to the high-affinity binding site of aspirin. The other one was found in fragment C. Acetylation of albumin brings about marked conformational change in the protein, which probably accounts for the decrease in its ability to react with anti-HSA antibody. Bilirubin does not change the secondary structure of albumin but, like aspirin, lowers its antigenicity. It has been suggested that the decrease in antigenic properties in this case results from cooperation of the closely neighboring antigenic and bilirubin-binding sites. The studies of the influence of iron(III) tetrasulfonated phthalocyanine on bilirubin binding by HSA suggest that there is no competition between strong sites for iron(III) tetrasulfonated phthalocyanine and bilirubin, but these compounds compete for some of the weaker sites.
通过差示光谱法和圆二色性测量研究了胆红素与阿司匹林修饰的人血清白蛋白（HSA）的相互作用以及四磺化酞菁铁对天然蛋白质结合胆红素的影响。与含有天然蛋白质的类似体系相比，对含有胆红素和阿司匹林修饰的HSA的体系进行的光谱研究表明，白蛋白在赖氨酸199处的选择性乙酰化抑制了该蛋白质与胆红素的结合。在这两种情况下，胆红素与白蛋白之间的相互作用都会导致配体与蛋白质的摩尔比为2:1时形成复合物。对胆红素与经CNBr反应产生的白蛋白片段的反应研究表明，一个强胆红素结合位点位于M片段中，且靠近阿司匹林的高亲和力结合位点。另一个在C片段中发现。白蛋白的乙酰化导致蛋白质发生明显的构象变化，这可能是其与抗HSA抗体反应能力下降的原因。胆红素不会改变白蛋白的二级结构，但与阿司匹林一样，会降低其抗原性。有人认为，在这种情况下抗原特性的降低是由于相邻的抗原位点和胆红素结合位点相互作用的结果。对四磺化酞菁铁对HSA结合胆红素影响的研究表明，四磺化酞菁铁的强结合位点与胆红素之间不存在竞争，但这些化合物会竞争一些较弱的位点。
