This system relies on a small protein called “ubiquitin.” When a protein is to be targeted for destruction, enzymes called ubiquitin ligases chemically link a chain of ubiquitins to it. These serve as a tag that is recognized by enzymes that digest any proteins with ubiquitin attached to them.
So, the idea behind the new work is to identify a key viral protein and figure out how to attach ubiquitin to it. The cell would then take care of the rest, digesting the viral protein and thus blocking the production of any useful viruses in that cell. In this case, the researchers decided to target the spike protein that sits on the surface of coronaviruses and allows them to attach to and infect new cells.
Unfortunately, there are no proteins that attach ubiquitin to the viral spike protein. Or, rather, there were no proteins that fit that description.
But a team at Harvard has now produced one.