Role of 尾/未101Gln in Regulating the Effect of Temperature and Allosteric Effectors on Oxygen Affinity in Woolly Mammoth Hemoglobin

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• 作者：Yue Yuan ; Catherine Byrd ; Tong-Jian Shen ; Virgil Simplaceanu ; Tsuey Chyi S. Tam ; Chien Ho
• 刊名：Biochemistry
• 出版年：2013
• 出版时间：December 10, 2013
• 年：2013
• 卷：52
• 期：49
• 页码：8888-8897
• 全文大小：436K
• 年卷期：v.52,no.49(December 10, 2013)
• ISSN：1520-4995

文摘

The oxygen affinity of woolly mammoth hemoglobin (rHb WM) is less affected by temperature change than that of Asian elephant hemoglobin (rHb AE) or human normal adult hemoglobin (Hb A). We report here a biochemical鈥揵iophysical study of Hb A, rHb AE, rHb WM, and three rHb WM mutants with amino acid substitutions at 尾/未101 (尾/未101Gln鈫扜lu, Lys, or Asp) plus a double and a triple mutant, designed to clarify the role of the 尾/未101 residue. The 尾/未101Gln residue is important for responding to allosteric effectors, such as phosphate, inositol hexaphosphate (IHP), and chloride. The rHb WM mutants studied generally have higher affinity for oxygen under various conditions of pH, temperature, and salt concentration, and in the presence or absence of organic phosphate, than do rHb WM, rHb AE, and Hb A. Titrations for the O₂ affinity of these mutant rHbs as a function of chloride concentration indicate a lower heterotopic effect of this anion due to the replacement of 尾/未101Gln in rHb WM. The alkaline Bohr effect of rHb WM and its mutants is reduced by 20鈥?0% compared to that of Hb A and is independent of changes in temperature, in contrast to what has been observed in the hemoglobins of most mammalian species, including human. The results of our study on the temperature dependence of the O₂ affinity of rHb WM and its mutant rHbs illustrate the important role of 尾/未101Gln in regulating the functional properties of these hemoglobins.