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Calorimetric study of a series of designed repeat proteins: Modular structure and modular folding
Author(s) -
Cortajarena Aitziber L.,
Regan Lynne
Publication year - 2011
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.564
Subject(s) - tetratricopeptide , protein folding , contact order , structural motif , modular design , chemistry , folding (dsp implementation) , crystallography , protein structure , protein secondary structure , computational biology , native state , biology , computer science , biochemistry , electrical engineering , gene , engineering , operating system
Repeat proteins comprise tandem arrays of a small structural motif. Their structure is defined and stabilized by interactions between residues that are close in the primary sequence. Several studies have investigated whether their structural modularity translates into modular thermodynamic properties. Tetratricopeptide repeat proteins (TPRs) are a class in which the repeated unit is a 34 amino acid helix‐turn‐helix motif. In this work, we use differential scanning calorimetry (DSC) to study the equilibrium stability of a series of TPR proteins with different numbers of an identical consensus repeat, from 2 to 20, CTPRa2 to CTPRa20. The DSC data provides direct evidence that the folding/unfolding transition of CTPR proteins does not fit a two‐state folding model. Our results confirm and expand earlier studies on TPR proteins, which showed that apparent two‐state unfolding curves are better fit by linear statistical mechanics models: 1D Ising models in which each repeat is treated as an independent folding unit.