Noun
polyubiquitin (plural polyubiquitins)
(biochemistry) A chain of several ubiquitin molecules attached to a protein.
Following addition of a single ubiquitin moiety to a protein substrate, further ubiquitin molecules can be added to the first, yielding a polyubiquitin chain. Source: Internet
Like monoubiquitination, lysine 63-linked polyubiquitin chains also has a role in the trafficking some membrane proteins. Source: Internet
Ubiquitin is either expressed as multiple copies joined in a chain (polyubiquitin) or attached to ribosomal subunits. Source: Internet