Protein folding from a combinatorial perspective.

Combinatorial mutagenesis experiments show the existence of many different solutions to the problem of complementary packing of non-polar sidechains in the protein core. They suggest that a significant amount of structural information is carried by the simple pattern of polar and non-polar residues along the polypeptide chain, indicate that the formation of buried polar interactions may be a fundamentally slow step in protein folding and show that proteins with many native properties occur at reasonable frequencies in random sequence libraries.