Ubiquitin is called so as:
Ubiquitin, so named because it is present in all eukaryotic cells, is a small (8.5 kDa, 76 residues) polypeptide that targets many intracellular proteins for degradation. The primary structure of ubiquitin is highly conserved. Ref: Harper 28th edition, chapter 28.
Present in all eukaryotic cells
Takes pa in impoant reactions
Is highly conserved
None of the above