Regis Wiliam C B, Fattori Juliana, Santoro Marcelo M, Jamin Marc, Ramos Carlos H I
Centro de Biologia Molecular Estrutural, Laboratório Nacional de Luz Síncrotron, P.O. Box 6192, ZIP Code 13084971, Campinas SP, Brazil.
Arch Biochem Biophys. 2005 Apr 1;436(1):168-77. doi: 10.1016/j.abb.2005.01.016.
The work in the literature on apomyoglobin is almost equally divided between horse and sperm whale myoglobins. The two proteins share high homology, show similar folding behavior, and it is often assumed that all folding phenomena found with one protein will also be found with the other. We report data at equilibrium showing that horse myoglobin was 2.1 kcal/mol less stable than sperm whale myoglobin at pH 5.0, and aggregated at high concentrations as measured by gel filtration and analytical ultracentrifugation experiments. The higher stability of sperm whale myoglobin was identified for both apo and holo forms, and was independent of pH from 5 to 8 and of the presence of sodium chloride. We also show that the substitution of sperm whale myoglobin residues Ala15 and Ala74 to Gly, the residues found at positions 15 and 74 in horse myoglobin, decreased the stability by 1.0 kcal/mol, indicating that helix propensity is an important component of the explanation for the difference in stability between the two proteins.
文献中关于脱辅基肌红蛋白的研究工作，几乎在马肌红蛋白和抹香鲸肌红蛋白之间平均分配。这两种蛋白质具有高度同源性，表现出相似的折叠行为，并且人们常常认为，在一种蛋白质中发现的所有折叠现象，在另一种蛋白质中也会出现。我们报告了在平衡状态下的数据，结果显示，在pH 5.0时，马肌红蛋白的稳定性比抹香鲸肌红蛋白低2.1千卡/摩尔，并且通过凝胶过滤和分析超速离心实验测量发现，在高浓度时马肌红蛋白会聚集。对于脱辅基和全蛋白形式的抹香鲸肌红蛋白，都确定了其较高的稳定性，并且该稳定性在pH值从5到8以及存在氯化钠的情况下均不受影响。我们还表明，将抹香鲸肌红蛋白的Ala15和Ala74残基替换为马肌红蛋白中15和74位的甘氨酸残基，会使稳定性降低1.0千卡/摩尔，这表明螺旋倾向是解释这两种蛋白质稳定性差异的一个重要因素。
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