PROTEIN FOLDS - TOWARDS UNDERSTANDING FOLDING FROM INSPECTION OF NATIVE STRUCTURES

Following a short summary of some of the principal features of folded proteins, the results of two complementary studies of protein structur e are presented, the first concerned with the factors which influence secondary structure propensity and the second an analysis of protein t opology. In an attempt to deconvolute the physical contributions to se condary structure propensities, we have calculated intrinsic phi, psi propensities, derived from the coil regions of proteins. Comparison of intrinsic phi, psi propensities with their equivalent secondary struc ture values show correlations for both helix and strand. This suggests that the local dipeptide, steric and electrostatic interactions have a major influence on secondary structure propensity. We then proceed t o inspect the distribution of protein domain folds observed to date. S everal folds occur very commonly, so that 46% of the current non-homol ogous database comprises only nine folds. The implications of these re sults for protein folding are discussed.