So we see that the proteosome consists of a core of 20s subunit and 219s subunits position at both ends of this core. Now, the 19s subunits are the regulatory units and the 20s are the catalytic subunits. So in a way you can imagine that the 20s subunit is like a garbage disposal. It basically churns and breaks down that protein into smaller peptides while the 19s subunits basically bind to the poly ubiquitinated protein and they protect other proteins from actually entering the core and being broken down. So if we look at the steps that involve this process, we can summarize the steps in this diagram. So let's suppose we have some protein shown here.