Mapping the energy landscape of repeat proteins using NMR-detected hydrogen exchange

JOURNAL OF MOLECULAR BIOLOGY

卷:379

Article

Cortajarena, Aitziber L.¹  Mochrie, Simon G. J.^2,3  Regan, Lynne^1,4 

[1] Yale Univ, Dept Mol Biophys & Biochem, New Haven, CT 06520 USA

[2] Yale Univ, Dept Phys, New Haven, CT 06520 USA

[3] Yale Univ, Dept Appl Phys, New Haven, CT 06520 USA

[4] Yale Univ, Dept Chem, New Haven, CT 06520 USA

关键词: native-state hydrogen exchange;    protein folding;    tetratricopeptide repeat (TPR);    1D-Ising model;    partially unfolded form;   

DOI  :  10.1016/j.jmb.2008.02.046

来源: Elsevier

【 摘 要 】

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.

【 授权许可】

Free