Mapping the energy landscape of repeat proteins using NMR-detected hydrogen exchange
Mapping the energy landscape of repeat proteins using NMR-detected hydrogen exchange
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DOI：
10.1016/j.jmb.2008.02.046
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发表时间：
2008-06-06
影响因子：
5.6
通讯作者：
Regan, Lynne
中科院分区：
文献类型：
--
作者：
Cortajarena, Aitziber L.;Mochrie, Simon G. J.;Regan, Lynne
重复蛋白质包含简单结构基序的串联阵列。与球状蛋白质相反，重复蛋白质仅通过序列中相对靠近的残基之间的相互作用而稳定，而没有“长程”相互作用。我们的工作集中在tetratricopeptide repeat（TPR），一个34个氨基酸的螺旋-转角-螺旋基序，在许多天然蛋白质的串联阵列中发现。早些时候，我们报道了一系列共有TPR（CTPR）蛋白的设计和表征，这些蛋白构建为34个氨基酸共有序列的多个串联拷贝的阵列。在这里，我们提出了广泛的氢交换（HX）研究的两个CTPR蛋白（CTPR 2和CTPR 3）的折叠-展开行为的结果。我们使用HX来检测和表征部分折叠的物种，这些物种在名义上的折叠状态下以低频率填充。我们发现，这两种蛋白质的平衡折叠展开过渡是非两个状态，但顺序，与最外层的螺旋显示出显着更高的概率比内螺旋被展开。我们表明，实验观察到的展开行为是一个简单的伊辛模型，其中个别螺旋被视为“自旋等价物”的预测是一致的。我们提出的结果具有普遍的影响，我们的理解重复蛋白质的热力学性质。(c)2008爱思唯尔有限公司保留所有权利。
Repeat proteins contain tandem arrays of a simple structural motif. In contrast to globular proteins, repeat proteins are stabilized only by interactions between residues that are relatively close together in the sequence, with no "long-range" interactions. Our work focuses on the tetratricopeptide repeat (TPR), a 34 amino acid helix-turn-helix motif found in tandem arrays in many natural proteins. Earlier, we reported the design and characterization of a series of consensus TPR (CTPR) proteins, which are built as arrays of multiple tandem copies of a 34 amino acid consensus sequence. Here, we present the results of extensive hydrogen exchange (HX) studies of the folding-unfolding behavior of two CTPR proteins (CTPR2 and CTPR3). We used HX to detect and characterize partially folded species that are populated at low frequency in the nominally folded state. We show that for both proteins the equilibrium folding-unfolding transition is non-two-state, but sequential, with the outermost helices showing a significantly higher probability than inner helices of being unfolded. We show that the experimentally observed unfolding behavior is consistent with the predictions of a simple Ising model, in which individual helices are treated as "spin-equivalents". The results that we present have general implications for our understanding of the thermodynamic properties of repeat proteins. (c) 2008 Elsevier Ltd. All rights reserved.