Origins of chevron rollovers in non-two-state protein folding kinetics.

Chevron rollovers of some proteins imply that their logarithmic folding rates are nonlinear in native stability. This is predicted by lattice and continuum Gō models to arise from diminished accessibilities of the ground state from transiently populated compact conformations under strongly native conditions. Despite these models' native-centric interactions, the slowdown is due partly to kinetic trapping caused by some of the folding intermediates' non-native topologies. Notably, simple two-state folding kinetics of small single-domain proteins are not reproduced by common Gō-like schemes.