Neighbor effect on PPII conformation in alanine peptides
Neighbor effect on PPII conformation in alanine peptides
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DOI：
10.1021/ja052094o
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发表时间：
2005-07-27
影响因子：
15
通讯作者：
Kallenbach, NR
中科院分区：
文献类型：
--
作者：
Chen, K;Liu, ZG;Kallenbach, NR
聚脯氨酸 II (PPII) 构象在短丙氨酸寡聚物中占主导地位。丙氨酸肽中PPII结构的非协同性表明水中的PPII是局部决定的并且丙氨酸邻居与Flory的孤立对假说一致。然而，如线圈库数据中观察到的，来自 β 支链或庞大芳香族残基的邻近效应往往会增加最近邻的 Φ 角。在这里，我们使用短丙氨酸模型肽 GGAAAGG、GGLnALnGG（Lnis 正亮氨酸）、GGIAAGG 和 GGIAIGG 直接证明了邻近效应。远紫外CD光谱、NMR3JαN耦合常数和HD氢交换测量表明，相对于Ala或norLeu，Ile降低了探针Ala侧链的PPII含量。自由能差异与静电溶剂化自由能 (ESF) 计算的预测一致。结果表明，PPII 倾向或量表的预测需要包括邻居效应。
The polyproline II (PPII) conformation is dominant in short alanine oligomers. The noncooperativity of PPII structure in alanine peptides indicates that PPII in water is locally determined and that alanine neighbors are consistent with Flory's isolated pair hypothesis. However, neighbor effects from β-branched or bulky aromatic residues tend to increase the Φ angle of the nearest neighbor as observed in coil library data. Here we demonstrate directly the neighbor effect using short alanine model peptides GGAAAGG, GGLnALnGG (Lnis norleucine), GGIAAGG, and GGIAIGG. The far-UV CD spectra, NMR3JαNcoupling constant, and H−D hydrogen exchange measurements reveal that Ile reduces the PPII content of the probe Ala side chain relative to Ala or norLeu. The free energy differences are consistent with predictions from electrostatic solvation free energy (ESF) calculations. The results indicate that prediction of PPII propensities or scales requires including the neighbor effect.