Conformational analysis of a chain reversal in alpha-chymotrypsin

A complete conformational analysis of the fold (Asp-Lys-Thr-Gly) (residues 35-38), and additional adjacent residues of alpha-chymotrypsin has been performed. A comparison of these findings with those of Lewis et al. (1) is made, and a discussion of the implications of protein-fold models is discussed. This particular residue sequence prefers to bend over maintaining a helical conformation. However, the bend conformation of the tetramer is different from that of the native bend. The native bend conformation is nearly realized when an additional residue of the native primary structure is added to each side of the tetramer. Early and late folding-sequence studies suggests that while the native fold is of low energy, there are fold-points along the primary structure which are more stable. The structural implications of this finding are discussed.