Protein Unfolding by Prokaryotic Energy Dependent Proteases

Northwestern University, Evanston IL

Investigators

Abstract

Folding of protein chains into specific three-dimensional shapes is essential for performing their biological function. However, there are essential processes in the cell for which proteins must unfold again, such as when damaged or regulatory proteins are removed by enzymes called ATP-dependent proteases. Failure to remove regulatory proteins can lead to malfunctioning of cellular processes, often leading to cell death. This project investigates how ATP-dependent proteases unfold and degrade proteins. ATP-dependent proteases represent a new and exciting type of molecular machine. They are interesting because of the central role they play in cellular regulation and because they catalyze a complex process with novel mechanistic features. Some ATP-dependent proteases degrade proteins by sequentially unraveling their substrates from a degradation tag. The proteases mechanically unfold proteins at their surface and then translocate the polypeptide chain over a distance to the active sites of proteolysis. The proteases appear to pull at the substrates' polypeptide chains. New aspects of this mechanism are investigated. At least four classes of ATP-dependent proteases exist. Their properties and mechanisms are compared and the biological consequences of differences in the unfolding activity analyzed. The mechanism of unfolding by pulling is not restricted to proteases but can be found in the action of other biological machines, specifically protein translocases. Thus, understanding the mechanism of protein unfolding by pulling is of broad biological interest and significance. Broader Impacts: Dissemination of knowledge and teaching are also important aspects of this project. Undergraduates from the College of Arts and Sciences and the School of Engineering as well as students from local high schools are involved in the project. The project will also involve outreach to a local primary school (K-8).