PREDICTING LEUCINE-ZIPPER STRUCTURES FROM SEQUENCE

The leucine zipper structure is adopted by one family of the coiled co il proteins, Leucine zippers have a characteristic leucine repeat: Leu -X(6)-Leu-X(6)-Leu-X(6)-Leu (where X may be any residue), However, man y sequences have the leucine repeat, but do not adopt the leucine zipp er structure (we shall refer to these as non-zippers), We have found a nd analyzed residue pair patterns that allow one to identify correctly 90% of leucine zippers and 97% of non-zippers, Simpler analyses, base d on the frequency of occurrence of residues at certain positions, spe cify, at most, 65% of zippers and 80-90% of non-zippers, Both short an d long patterns contribute to the successful discrimination of leucine zippers from non-zippers, A number of these patterns involve hydropho bic residues that would be placed on the solvent-exposed surface of th e helix, were the sequence to adopt a leucine zipper structure, Thus, an analysis of protein sequences has allowed us to improve discriminat ion between leucine zippers and non-zippers, and has provided some fur ther insight into the physical factors influencing the leucine zipper structure.