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“Invisible” Conformers of an Antifungal Disulfide Protein Revealed by Constrained Cold and Heat Unfolding, CEST‐NMR Experiments, and Molecular Dynamics Calculations
Author(s) -
Fizil Ádám,
Gáspári Zoltán,
Barna Terézia,
Marx Florentine,
Batta Gyula
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201404879
Subject(s) - conformational isomerism , chemistry , chemical shift , molecular dynamics , population , conformational ensembles , nuclear magnetic resonance spectroscopy , crystallography , computational chemistry , stereochemistry , molecule , organic chemistry , demography , sociology
Transition between conformational states in proteins is being recognized as a possible key factor of function. In support of this, hidden dynamic NMR structures were detected in several cases up to populations of a few percent. Here, we show by two‐ and three‐state analysis of thermal unfolding, that the population of hidden states may weight 20–40 % at 298 K in a disulfide‐rich protein. In addition, sensitive 15 N‐CEST NMR experiments identified a low populated (0.15 %) state that was in slow exchange with the folded PAF protein. Remarkably, other techniques failed to identify the rest of the NMR “dark matter”. Comparison of the temperature dependence of chemical shifts from experiments and molecular dynamics calculations suggests that hidden conformers of PAF differ in the loop and terminal regions and are most similar in the evolutionary conserved core. Our observations point to the existence of a complex conformational landscape with multiple conformational states in dynamic equilibrium, with diverse exchange rates presumably responsible for the completely hidden nature of a considerable fraction.