| Downhill protein folding, i.e., folding with the free energy barrier comparable to the thermal energy kBT, is investigated by combining laser induced temperature-jump kinetics measurements and Langevin dynamics simulations. A kinetic and thermodynamic survey of multiple WW domain mutants is performed in combination with a model to reveal the correlation between protein stability and downhill folding propensity. A designed histidine containing lambda repressor mutant is identified to be a downhill folder even at its melting temperature, showing both thermodynamic and kinetic signatures of downhill folding for the first time. All the reported downhill folders are classified based on their typical downhill folding free energy building blocks using Langevin dynamics simulations. |
