Physiological changes in the albumin-bound non-esterified free fatty acids critically influence heme/bilirubin binding properties of the protein: A comparative, in vitro, spectroscopic study using the endogenous biomolecules
Physiological changes in the albumin-bound non-esterified free fatty acids critically influence heme/bilirubin binding properties of the protein: A comparative, in vitro, spectroscopic study using the endogenous biomolecules
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DOI：
10.1016/j.saa.2020.118298
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发表时间：
2020-07-05
影响因子：
4.4
通讯作者：
Khodarahmi, Reza
中科院分区：
文献类型：
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作者：
Amoorahim, Mahtab;Ashrafi-Kooshk, Mohammad Reza;Khodarahmi, Reza
血红素和胆红素(BR)是红细胞(和血红蛋白)降解的副产品，在某些疾病中显示出血浆浓度升高。这两种有毒的疏水分子主要通过携带多种配体的人血清白蛋白(HSA)在血流中运输。在正常生理条件下，每个HSA都与3个脂肪酸(FA)分子结合，其对BR/血红素结合的可能作用尚不清楚。在本研究中，为了更深入地了解这一问题，我们从血浆FA水平正常的健康个体中提纯了白蛋白(作为纯化的非脱脂白蛋白或PA)，然后脱脂了部分纯化的蛋白(作为脱脂的HSA或DA)。在下一步中，利用各种光谱方法，研究了它们与血红素和BR的相互作用。通过1：1的配体结合、猝灭和热力学参数分析表明，胆红素和血红素与PA和DA的结合常数(K-b)值不同。可以看出，高亲和力FA结合位点(FABS)中FA的存在显著改变了结构的构象，随后改善了BR结合，同时阻碍了血红素的相互作用。通过测定纯化白蛋白(PA)和DA的表面疏水性证实了这一数据，并通过生物信息学分析进行了支持。对观察到的动态相互作用的生理和临床相关性也进行了讨论。这项研究也再次证实了BR的主要结合位点是IIA亚域而不是IB亚域。(C)2020爱思唯尔B.V.保留所有权利。
Heme and bilirubin (BR), as by-products of red blood cells (and hemoglobin) degradation, show increased plasma concentrations in some diseases. These two toxic hydrophobic molecules are mainly transported in the blood-stream by human serum albumin (HSA) that carries a wide variety of ligands. Under normal physiological conditions, similar to 3 fatty acid (FA) molecules are bound to each HSA; and its possible effect on BR/heme binding remains to be more clarified. In the present study, to provide deeper insight on this issue, we purified albumin from healthy individuals (as purified non-defatted albumin or PA) with normal plasma levels of FA, then defatted some of the purified protein (as defatted-HSA; or DA). In the next step, using various spectroscopic methods, their interactions with heme and BR were investigated. By 1: 1 binding of the ligands, quenching and thermodynamic analysis of parameters indicated that binding constants (K-b) values of bilirubin and heme for PA and DA are different. It could be perceived that the presence of FAs in high-affinity FA binding sites (FABSs) exerted considerable conformational changes in the structure followed by an improved BR binding while hindered heme interaction. The data was confirmed by determining surface hydrophobicity of the purified albumin (PA) and DA, and then supported by bioinformatics analyses. The physiological and clinical relevance of the observed dynamic interactions is also discussed. This study, also, re-confirmed that the primary BR binding site is subdomain IIA not subdomain IB. (C) 2020 Elsevier B.V. All rights reserved.