Biophysical characterization of the α-globin binding protein α-hemoglobin stabilizing protein
Biophysical characterization of the α-globin binding protein α-hemoglobin stabilizing protein
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DOI：
10.1074/jbc.m206084200
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发表时间：
2002-10-25
影响因子：
4.8
通讯作者：
Mackay, JP
中科院分区：
文献类型：
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作者：
Gell, D;Kong, Y;Mackay, JP
α-血红蛋白稳定蛋白（α-Hemoglobin Stabilizing Protein，AHSP）是一种小分子量（12 kDa）、丰富的红系特异性蛋白质，能特异性结合游离的α-血红蛋白并阻止其沉淀。当α-珠蛋白过量存在于β-珠蛋白（其正常结合伴侣）时，α-珠蛋白可具有严重的细胞毒性作用，导致重要的人类疾病，如β-地中海贫血。由于血红蛋白稳定蛋白可能作为一种伴侣蛋白，以防止在正常红系细胞发育过程中和珠蛋白链失衡疾病中α-珠蛋白的有害聚集，因此重要的是要表征血红蛋白稳定蛋白的生化特性（.）α-珠蛋白复合物在这里，我们提供了关于α-血红蛋白稳定蛋白及其与α-珠蛋白相互作用的第一个结构信息。我们发现α-血红蛋白稳定蛋白是一种主要的α-螺旋球状蛋白，形状有些不对称。α-血红蛋白稳定蛋白和α-珠蛋白在溶液中都是单体，通过分析超离心法测定，并通过凝胶过滤和氨基酸分析判断，相互结合形成1：1亚基化学计量的复合物。我们用等温滴定量热法表明，这种相互作用具有中等亲和力，结合常数为1 × 10（7）M-1，因此，考虑到晚期原成红细胞中α-血红蛋白稳定蛋白（近似于0.1 mM）和血红蛋白（近似于4 mM）的浓度，这种相互作用可能具有生物学意义。
alpha-Hemoglobin stabilizing protein (AHSP) is a small (12 kDa) and abundant erythroid-specific protein that binds specifically to free alpha-(hemo)globin and prevents its precipitation. When present in excess over beta-globin, its normal binding partner, alpha-globin can have severe cytotoxic effects that contribute to important human diseases such as beta-thalassemia. Because AHSP might act as a chaperone to prevent the harmful aggregation of alpha-globin during normal erythroid cell development and in diseases of globin chain imbalance, it is important to characterize the biochemical properties of the AHSP(.)alpha-globin complex. Here we provide the first structural information about AHSP and its interaction with a-globin. We find that AHSP is a predominantly alpha-helical globular protein with a somewhat asymmetric shape. AHSP and alpha-globin are both monomeric in solution as determined by analytical ultracentrifugation and bind each other to form a complex with 1:1 subunit stoichiometry, as judged by gel filtration and amino acid analysis. We have used isothermal titration calorimetry to show that the interaction is of moderate affinity with an association constant of I X 10(7) M-1 and is thus likely to be biologically significant given the concentration of AHSP (similar to0.1 mm) and hemoglobin (similar to4 mm) in the late pro-erythroblast.