The effect of the polyproline II (PPII) conformation on the denatured state entropy
The effect of the polyproline II (PPII) conformation on the denatured state entropy
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DOI：
10.1110/ps.0237803
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发表时间：
2003-03-01
期刊：
影响因子：
8
通讯作者：
Hilser, VJ
中科院分区：
文献类型：
--
作者：
Ferreon, JC;Hilser, VJ
据报道，聚脯氨酸II（PPII）是肽的未折叠状态下的主要构象，即使序列中不存在脯氨酸。在这里，我们使用等温滴定量热法（ITC）调查的PPII偏差在未折叠状态下，通过研究结合的SH 3结构域的SEM-5的变体，其假定的PPII肽配体，Sos。该实验系统是独特的，因为它提供了直接访问的取代的氨基酸的构象熵变。结果表明，变性合奏的特征在于至少有两个philically不同的状态，PPII的构象和未折叠的状态，符合先前持有的想法的变性状态作为一个随机收集的构象主要由硬球碰撞。丙氨酸和甘氨酸在变性状态下的PPII构象的概率被发现是显着的，分别接近30%和接近10%，导致折叠的构象熵显着降低。
Polyproline II (PPII) is reported to be a dominant conformation in the unfolded state of peptides, even when no prolines are present in the sequence. Here we use isothermal titration calorimetry (ITC) to investigate the PPII bias in the unfolded state by studying the binding of the SH3 domain of SEM-5 to variants of its putative PPII peptide ligand, Sos. The experimental system is unique in that it provides direct access to the conformational entropy change of the substituted amino acids. Results indicate that the denatured ensemble can be characterized by at least two thermodynamically distinct states, the PPII conformation and an unfolded state conforming to the previously held idea of the denatured state as a random collection of conformations determined largely by hard-sphere collision. The probability of the PPII conformation in the denatured states for Ala and Gly were found to be significant, similar to30% and similar to10%, respectively, resulting in a dramatic reduction in the conformational entropy of folding.