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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Subunit Disassembly Pathway of Human Hemoglobin Revealing the Site-Specific Role of Its Cysteine Residues
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Subunit Disassembly Pathway of Human Hemoglobin Revealing the Site-Specific Role of Its Cysteine Residues

机译：人类血红蛋白的亚基拆卸途径揭示了其半胱氨酸残基的位点特异性作用

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摘要

Cysteine residues play a unique role in human hemoglobin (Hb) by affecting its cooperative oxygen binding behavior and the stability of its tetrameric structure. However, how these cysteine residues fulfill their biophysical functions from the molecular level is yet unclear. Here we study the subunit disassembly pathway of human hemoglobin using the sulfhydryl reagent, p-hydroxymercuribenzoate (PMB) and investigate the functional roles of cysteine residues in human hemoglobin. We show evidence from the matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry that all three types of cysteine residues, including the surface-exposed βCys93 and the shielded αCys104 and βCysll2 are reactive to PMB, resolving an issue long under debate. It is demonstrated that all three types of cysteine residues must be blocked by PMB to accomplish the subunit disassembly, and the PMB-cysteine reactions proceed in a stepwise manner with an order of βCys93, αCysl04, and βCys112. The PMB reactions with the three different cysteine residues demonstrate strong site-specificity. The possible influence of PMB-cysteine reactions to the stability of various intersubunit salt bridges has been discussed based on the crystallographic structure of hemoglobin, providing insights in' understanding the hemoglobin subunit disassembly pathway and the site-specific functional role of each cysteine residue in hemoglobin.
机译：半胱氨酸残基通过影响其协同氧结合行为及其四聚体结构的稳定性在人血红蛋白（Hb）中发挥独特作用。然而，尚不清楚这些半胱氨酸残基如何从分子水平上实现其生物物理功能。在这里，我们研究了使用巯基试剂对羟基巯基苯甲酸酯（PMB）的人类血红蛋白亚基拆卸途径，并研究了半胱氨酸残基在人类血红蛋白中的功能作用。我们从基质辅助激光解吸电离飞行时间（MALDI-TOF）质谱中获得的证据表明，所有三种类型的半胱氨酸残基，包括表面暴露的βCys93和被屏蔽的αCys104和βCysll2均与PMB反应，从而解决了这个问题长期处于辩论之中。已经证明，所有三种类型的半胱氨酸残基都必须被PMB封闭才能完成亚基的拆卸，并且PMB-半胱氨酸反应以βCys93，αCysl04和βCys112的顺序逐步进行。具有三个不同半胱氨酸残基的PMB反应显示出很强的位点特异性。基于血红蛋白的晶体结构，讨论了PMB-半胱氨酸反应对各种亚基间盐桥稳定性的可能影响，为深入了解血红蛋白亚基分解途径和每个半胱氨酸残基在血红蛋白中的位点特异性功能提供了见识。 。

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