The Role of Sequence and Structure in Protein Folding Kinetics: the Diffusion-Collision Model Applied to Proteins L and G

The diffusion-collision model (DCM) is applied to the folding kinetics of protein L and protein G.  In the DCM, the two proteins are treated as consisting of two beta-hairpins and one alpha-helix, so that they are isomorphous with the three-helix bundle DCM model.  In the absence of sequence dependent factors, both proteins would fold in the same way in the DCM, with the coalescence of the N-terminal hairpin and the helix slightly favored over the C-terminal hairpin and the helix because the former are closer together than the latter.  However, sequence dependent factors make the N-terminal hairpin of protein L and the C-terminal hairpin of protein G more stable in the ensemble of unfolded conformations.  This difference in the stabilities gives rise to the difference in the calcd. folding behavior, in agreement with expt.