Hemoglobin (Hb) is a major oxygen-transporting protein with allosteric properties reflected in the structural changes that accompany binding of O2. Glycated hemoglobin (GHb), which is a minor component of human red cell hemolysate, is generated by a nonenzymatic reaction between glucose and hemoglobin. Due to the long lifetime of human erythrocytes (∼120 days), GHb is widely used as a reliable biomarker for monitoring long-term glucose control in diabetic patients. Although the structure of GHb differs from that of Hb, structural changes relating to the oxygen affinity of these proteins remain incompletely understood. In this study, the oxygen-binding kinetics of Hb and GHb are evaluated, and their structural dynamics are investigated using solution small-angle X-ray scattering (SAXS), electrospray ionization mass spectrometry equipped with ion mobility spectrometry (ESI-IM-MS), and molecular dynamic (MD) simulations to understand the impact of structural alteration on their oxygen-binding properties. Our results show that the oxygen-binding kinetics of GHb are diminished relative to those of Hb. ESI-IM-MS reveals structural differences between Hb and GHb, which indicate the preference of GHb for a more compact structure in the gas phase relative to Hb. MD simulations also reveal an enhancement of intramolecular interactions upon glycation of Hb. Therefore, the more rigid structure of GHb makes the conformational changes that facilitate oxygen capture more difficult creating a delay in the oxygen-binding process. Our multiple biophysical approaches provide a better understanding of the allosteric properties of hemoglobin that are reflected in the structural alterations accompanying oxygen binding.

中文翻译：

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血红蛋白中氧亲和相关结构变化的离子淌度质谱分析。

血红蛋白 (Hb) 是一种主要的氧转运蛋白，其变构特性反映在伴随 O2 结合的结构变化中。糖化血红蛋白 (GHb) 是人体红细胞溶血物中的次要成分，由葡萄糖和血红蛋白之间的非酶反应生成。由于人类红细胞的长寿命（~120 天），GHb 被广泛用作监测糖尿病患者长期血糖控制的可靠生物标志物。尽管 GHb 的结构与 Hb 的结构不同，但与这些蛋白质的氧亲和力相关的结构变化仍未完全了解。在这项研究中，评估了 Hb 和 GHb 的氧结合动力学，并使用溶液小角 X 射线散射 (SAXS) 研究了它们的结构动力学，配备离子迁移谱 (ESI-IM-MS) 的电喷雾电离质谱和分子动力学 (MD) 模拟以了解结构改变对其氧结合特性的影响。我们的结果表明，GHb 的氧结合动力学相对于 Hb 的氧结合动力学有所降低。ESI-IM-MS 揭示了 Hb 和 GHb 之间的结构差异，这表明 GHb 相对于 Hb 更倾向于气相中更紧凑的结构。MD 模拟还揭示了 Hb 糖基化后分子内相互作用的增强。因此，GHb 的更刚性结构使促进氧捕获的构象变化更加困难，从而延迟氧结合过程。