Open AccessPolyproline II propensities from GGXGG peptides reveal an anticorrelation with β-sheet scales
Author(s) -
Zhou Shi,
Chul Kang,
Zhigang Liu,
Angela Ng,
W. Clay Bracken,
Neville R. Kallenbach
Publication year - 2005
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0507124102
Subject(s) - polyproline helix , random coil , statistical mechanics , characterization (materials science) , chemistry , peptide , statistical physics , physics , materials science , crystallography , nanotechnology , circular dichroism , biochemistry
There is growing appreciation of the functional relevance of unfolded proteins in biology. However, unfolded states of proteins have proven inaccessible to the usual techniques for high-resolution structural and energetic characterization. Unfolded states are still generally conceived of as statistical coils, based on the pioneering work of Flory [(1969)Statistical Mechanics of Chain Molecules (Wiley, New York)] and Tanford [(1968)Adv. Protein Chem. 23, 121–282]. Recently, several lines of independent evidence have raised doubts about the random coil model and offer support for alternative views. Here, we show that polyproline II conformation is dominant in a host–guest peptide model AcGGXGGNH2 (X ≠ glycine), in equilibrium predominantly with β-structure. This result is inconsistent with a random coil model and the general view that these peptides are unstructured. By calculating a set of apparent ΔG values from the measured coupling constants of the backbone amides, we can construct a polyproline II scale that correlates negatively with β-sheet scales.