Soltys B J, Hsia J C
J Biol Chem. 1977 Jun 25;252(12):4043-8.
The introduction of a new spin-labeled anionic ligand, 1-gamma-aminobutyrate-5-N-(1-oxyl-2,2,6,6-tetramethyl-4-aminopiperidinyl)-2,4-dinitrobenzene, is reported. Under the experimental conditions, the first molar equivalent of this ligand is 93% bound to human serum albumin. With the addition of palmitate, the free spin label concentration decreases greatly, by almost 80%, in the presence of a fatty acid:albumin ratio of 3:1 to 4:1. The spectral characteristics of the bound spin label are also affected. The changes seen in the intensity of and the splitting between the high and low field extrema are indicative of perturbations of the protein molecule. It is seen then that the binding of each molar equivalent of fatty acid effects the conformation state of albumin and allosterically affects albumin binding properties. Computer spectral subtractions, furthermore, suggest that the binding of the first molar equivalent of palmitate specifically increases the affinity of the first two 1-gamma-amino-butyrate-5-N-(1-oxyl-2,2,6,6-tetramethyl-4-aminopiperidinyl)-2,4-dinitrobenzene binding sites. The present results indicate that fluctuations in serum free fatty acid levels within the physiological range may have a major modulatory effect on the free serum levels of certain drugs and/or physiological substances that bind to albumin.
报道了一种新的自旋标记阴离子配体，即1-γ-氨基丁酸-5-N-(1-氧基-2,2,6,6-四甲基-4-氨基哌啶基)-2,4-二硝基苯的引入。在实验条件下，该配体的第一个摩尔当量有93%与人血清白蛋白结合。加入棕榈酸后，在脂肪酸与白蛋白的比例为3:1至4:1的情况下，游离自旋标记物浓度大幅下降，几乎下降了80%。结合的自旋标记物的光谱特征也受到影响。高场和低场极值之间强度和分裂的变化表明蛋白质分子受到了扰动。由此可见，每摩尔当量脂肪酸的结合会影响白蛋白的构象状态，并通过变构作用影响白蛋白的结合特性。此外，计算机光谱减法表明，第一个摩尔当量棕榈酸的结合特异性地增加了前两个1-γ-氨基丁酸-5-N-(1-氧基-2,2,6,6-四甲基-4-氨基哌啶基)-2,4-二硝基苯结合位点的亲和力。目前的结果表明，生理范围内血清游离脂肪酸水平的波动可能对某些与白蛋白结合的药物和/或生理物质的游离血清水平产生主要的调节作用。
