In fact, we have to add at least four ubiquitous molecules to actually target that protein for degradation. And the way the Ubiquitin is added is in a process of manner. And what that means is once we attach that Ubiquitin onto this protein, we actually attach more ubiquitous molecules onto this ubiquitin. So once with this process happens, if we examine Ubiquitin, the 48th residue of Ubiquitin is a Lysine. And that Lysine is used in the same way that we use the Lysine of this target protein to basically attach a second Ubiquitin molecule in this same fashion here. So if we study the structure of Ubiquitin, ubiquitin at its 48th position will have a Lysine.