Substrate recognition and processing by the eukaryotic 26S proteasome (936.3)

Abstract

The 26S proteasome degrades a multitude of substrates and is essential for eukaryotic cell survival. The 2.5 mega‐dalton protease processes substrates through its 19S regulatory particle: this intricate complex binds, unfolds, and feeds substrates into the proteasomal peptidase, where they are irreversibly degraded. Although the mechanism of proteasome proteolysis has been well characterized, little is known about how the processing steps prior to degradation culminate to give an overall degradation rate. The complexity of substrate processing and the requisite of proteasome function for cell viability pose a significant challenge to quantitative analysis. I have developed an in vitro system to measure degradation and deubiquitination rates as a function of substrate thermodynamic stability and lysine placement. These tools lend insight on the rate limiting step in substrate degradation and how polyubiquitin tags are recognized and processed by this intricate proteolytic machine.Grant Funding Source: Supported by the National Science Foundation