Hemoglobinopathies are examples of autosomal recessive disorders of human hemoglobin. Hemoglobin E (HbE) and Hemoglobin D Punjab (HbD Punjab) are two of the most common hemoglobin variants geographically spread across Asian continent. These two variants differ from normal human hemoglobin (HbA) at a single amino acid residue caused by the point mutation of β globin gene. The presence of the mutated amino acid residue causes perturbation in the function of both variants. However, the structure–function correlation of these variants has not been established yet. In the present study, we analyzed the conformational changes associated with oxygenation of hemoglobin variants using hydrogen/deuterium exchange-based mass spectrometry of backbone amide hydrogens of α and β globin chains in the tetrameric hemoglobin molecule. We also performed the functional assay of these variants using oxygen dissociation equilibrium curve. Compared to HbA, both variants showed reduced oxygen affinity, as reported earlier. The functional perturbations exhibited by these variants were correlated well with their structural alterations with respect to the reported changes in the residue level interactions upon oxygenation of normal hemoglobin, monitored through the hydrogen/deuterium exchange kinetics of several peptic peptides originated from the isotopically exchanged oxy and deoxy forms of HbE and HbD Punjab.

中文翻译：

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点突变对血红蛋白变体，HbE和HbD Punjab的结构-功能相关性的影响。

血红蛋白病是人血红蛋白的常染色体隐性遗传疾病的例子。血红蛋白E（HbE）和血红蛋白D Punjab（HbD Punjab）是地理分布在亚洲大陆上的两种最常见的血红蛋白变体。这两个变体与正常人的血红蛋白（HbA）在一个由β珠蛋白基因的点突变引起的单个氨基酸残基上不同。突变的氨基酸残基的存在引起两种变体功能的扰动。然而，这些变体的结构-功能相关性尚未建立。在本研究中，我们使用基于氢/氘交换的四聚体血红蛋白分子中α和β血红蛋白链主链酰胺氢的氢/氘交换质谱分析了与血红蛋白变体氧化相关的构象变化。我们还使用氧离解平衡曲线对这些变异体进行了功能测定。如前所述，与HbA相比，两种变体均显示出降低的氧亲和力。这些变体表现出的功能性扰动与其结构改变有关，据报道，正常血红蛋白被氧合后，残基水平相互作用的变化已发生变化，这是通过几种源自同位素交换的氧和氧的消化性肽的氢/氘交换动力学来监测的。 HbE和HbD Punjab的脱氧形式。