| Modification Notes |
Ubiquitin is an abundant, highly conserved protein found in all eukaryotic cells either free or covalently attached to cellular proteins (1-3). The primary function of ubiquitin in mammalian systems is to clear abnormal, foreign and improperly folded proteins by targeting them for proteosome degradation (1-3). In the yeast, Saccharomyces cerevisiae, ubiquitin-like proteins include Rub1, Ula1, Uba3, Ubc12 and Ubc9 (4-5). Rub1 shares 53% homology with ubiquitin and requires activation via Ula1, Uba3 and Ubc12 in order to conjugate to substrates directed to different proteolytic systems (4). Skp1 connects cell cycle regulators to the ubiquitin proteolysis machinery (6). |