Noncharged amino acid residues at the solvent-exposed positions in the middle and at the C terminus of the α-helix have the same helical propensity
Noncharged amino acid residues at the solvent-exposed positions in the middle and at the C terminus of the α-helix have the same helical propensity
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DOI：
10.1110/ps.0304303
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发表时间：
2003-06-01
期刊：
影响因子：
8
通讯作者：
Makhatadze, GI
中科院分区：
文献类型：
--
作者：
Ermolenko, DN;Richardson, JM;Makhatadze, GI
先前已经确定，肽和蛋白质中α-螺旋中间的不同氨基酸残基的螺旋倾向非常相似。从已知的三维结构的蛋白质螺旋的统计分析表明，在中间和C末端的不带电残基的频率没有差异。然而，实验研究表明，在模型肽的中间和C末端的不带电残基的螺旋倾向的显着差异。这是一个普遍的影响，它是否适用于蛋白质螺旋或它是特定的模型丙氨酸为基础的肽？回答这个问题。通过使用差示扫描量热法测量遍在蛋白α-螺旋的28位（中间残基）和32位（C末端的C2位）的取代对该蛋白稳定性的影响。这两个数据集产生了相似的内在螺旋倾向值，从而得出结论，即在α-螺旋的中间和C末端的溶剂暴露位置处的不带电氨基酸残基具有相同的螺旋倾向。这一结论进一步支持了一个很好的相关性之间的螺旋倾向规模获得的两个位置在泛素与实验的螺旋倾向规模建立以前和蛋白质螺旋中的残基的统计分布。
It was established previously that helical propensities of different amino acid residues in the middle of alpha-helix in peptides and in proteins are very similar. The statistical analysis of the protein helices from the known three-dimensional structures shows no difference in the frequency of noncharged residues in the middle and at the C terminus. Yet, experimental studies show distinctive differences for the helical propensities of noncharged residues in the middle and in the C terminus in model peptides. Is this a general effect, and is it applicable to protein helices or is it specific to the model alanine-based peptides? To answer this question. the effects of substitutions at positions 28 (middle residue) and 32 (C2 position at the C terminus) of the alpha-helix of ubiquitin on the stability of this protein are measured by using differential scanning calorimetry. The two data sets produce similar values for intrinsic helix propensity, leading to a conclusion that noncharged amino acid residues at the solvent-exposed positions in the middle and at the C terminus of the alpha-helix have the same helical propensity. This conclusion is further supported with an excellent correlation between the helix propensity scale obtained for the two positions in ubiquitin with the experimental helix propensity scale established previously and with the statistical distribution of the residues in protein helices.