Biochemistry, Biology, Molecular Biology, Plant and Microbial Biosciences
University of Wisconsin-Madison
Our laboratory is attempting to elucidate the molecular mechanisms used by eukaryotes to selectively degrade intracellular proteins. Protein degradation has an integral role in cell maintenance, growth, and development and is an important component in the ability to genetically engineer organisms. Three fundamental questions are: (i) What are the pathways used to breakdown proteins and how are they selective? (ii) What specific functions does proteolysis have in cell physiology? And (iii) how can proteolysis be beneficially manipulated? One pathway of interest involves the conserved protein ubiquitin. It functions by becoming covalently attached to proteins targeted for catabolism, and then serves as a reusable recognition signal for target breakdown by the multisubunit 26S proteasome. We are studying this pathway by various approaches with special emphasis on the model plant, Arabidopsis thaliana. Of interest is a characterization of components involved in ubiquitin conjugation and an understanding of how these factors choose appropriate substrates. By reverse genetic methods, we are generating a wide array of mutants that should reveal the pathway’s function in Arabidopsis growth and development. As a model for selective proteolysis, we are also studying the form-dependent degradation of the morphogenic photoreceptor, phytochrome. This protein is unique in that its in vivo degradation rate by the ubiquitin pathway can be altered over 100 fold simply by illuminating plants with light.