Prevalence of the Diffusion Collision Model of Protein Folding In Vivo: A Mechanistic Analysis of the Acceleration of Protein Folding by Peptidyl-Prolyl Isomerase and the GroEL/ES Chaperonin System

This review assesses the differences between the diffusion-collision model and the extended nucleation condensation model of protein folding and attempts to determine; by analyzing the mechanisms through which peptidyl-prolyl isomerase and the GroEL/ES chaperonin system accelerate the rate of folding of their respective substrate proteins, which model of protein folding prevails <i>in vivo</i>. The difference in the kinetics between the two protein folding models was assessed in the introduction using free energy profiles which led to the identification of conditions that would favour one model over the other. Following the justification of the choice of chaperones used for analysis, the mechanism through which both chaperones accelerated the rate of folding of their respective proteins was investigated to determine whether the conditions developed by the chaperones were consistent with one model of protein folding over another. The review concludes with a summary of the key findings gleaned from mechanistic analysis of chaperone function and highlights its relevance to the biochemical and medical fields.