Helix-turn-helix motifs in unsolvated peptides
Helix-turn-helix motifs in unsolvated peptides
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DOI：
10.1021/ja0353006
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发表时间：
2003-06-18
影响因子：
15
通讯作者：
Jarrold, MF
中科院分区：
文献类型：
--
作者：
Kaleta, DT;Jarrold, MF
用离子迁移率测量和分子动力学模拟研究了非溶剂化Ac-A14 KG 3A 14 K +2 H+（Ac =乙酰基，A =丙氨酸，K =赖氨酸，G =甘氨酸）的构象.该肽被设计为模型螺旋-转角-螺旋基序。发现它采用三种不同的几何形状，它们被分配给仅在低温（<230 K）下稳定的延伸螺旋构象、相对高能量但具有交换赖氨酸的亚稳结构和卷曲螺旋。卷曲螺旋（由两个螺旋丙氨酸部分通过柔性甘氨酸环连接的反平行排列组成）是主要构象。当温度>350 K时，实验结果表明螺旋解偶，环随机化.从这个螺旋耦合→解耦合跃迁的平衡常数，我们发现ΔH° = −45 kJ mol-1和ΔS° = 114 J K-1 mol-1。−ΔH°本质上是两个螺旋对接在一起的焓变，而ΔS°本质上是释放甘氨酸环的熵变。
The conformations of unsolvated Ac-A14KG3A14K + 2H+(Ac = acetyl, A = alanine, K = lysine, G = glycine) have been examined by ion mobility measurements and molecular dynamics simulations. This peptide was designed as a model helix−turn−helix motif. It was found to adopt three distinct geometries which were assigned to an extended helical conformation which is only stable at low temperatures (<230 K), a relatively high energy but metastable structure with exchanged lysines, and a coiled-coil. The coiled coil (which consists of an antiparallel arrangement of two helical alanine sections linked by a flexible glycine loop) is the dominant conformation. For temperatures >350 K, the experimental results indicate the helices uncouple and the loop randomizes. From equilibrium constants determined for this helix coupling ⇄ uncoupling transition, we found ΔH° = −45 kJ mol-1and ΔS° = 114 J K-1mol-1. −ΔH° is essentially the enthalpy change for docking the two helices together while ΔS° is essentially the entropy change for freeing up the glycine loop.