Dimerization specificities of leucine zipper mutants

Abstract

The dimerization specificity of a leucine zipper is partially determined by the interactions of charged amino acids on the surfaces of dimer interfaces (e and g positions). A series of e and g position GCN4 mutants has been described that do not dimerize with the wild-type GCN4 but are able to dimerize with each other. Two hydrophobic leucine residues present in the wild-type GCN4 leucine zipper are suspected to be causing this difference in dimerization specificity. To determine the importance of these leucine residues in dimerization specificity, I constructed a series of mutants in which the leucine residues were substituted with alanine. The dimerization specificity of these mutants was determined based on the phenotypes of cells expressing wild-type and dominant negative λ repressor-leucine zipper fusion proteins. Cells that were immune to infection by phage λ contain homodimeric fusion proteins. Cells that were sensitive to infection by phage λ are forming heterodimeric fusion proteins. The two leucine residues in the wild-type GCN4 leucine zipper are not sufficient to explain the difference in dimerization specificity.