Genetic Dissection of the Specificity of Leucine Zipper Dimerization

Texas A&M Research Foundation, College Station TX

Investigators

Abstract

Leucine zippers are formed when a pair of short alpha -helices in a pair of protein molecules bind in a configuration called a coiled coil. Leucine zippers and other coiled coils are abundant in nature; they are found in about 10% of all proteins encoded in typical genomes, including many important transcription factors. The project addresses two complementary questions about leucine zippers. First, how do the subunit interactions in the context of a specific leucine zipper from the yeast transcription factor GCN4, control the specificity and stability of zipper assembly. Different interactions will be engineered into the GCN4 leucine zipper and characterized by biophysical assays including equilibrium and stopped-flow circular dichroism, sedimentation equilibrium, and X-ray crystallography. In addition, new biophysical assays for leucine zipper assembly will be implemented based on analytical ultracentrifugation and fluorescence correlation spectroscopy. Second, the project will explore the diversity of coiled coils in a whole genome. Using powerful genetic methods, the project will examine the specificity of interactions among hundreds of naturally occurring, predicted coiled-coils from the yeast genome that must coexist in the same cell. Because of their small size and simple, repetitive structures, leucine zippers have provided useful models for studying general issues in how proteins fold. By combining research on specific interactions with genome-wide studies of the properties of many zippers, this project will test whether our understanding of protein foldin is sufficient to illuminate the biology of a large and widely distributed class of important proteins.