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. Author manuscript; available in PMC: 2010 Jan 1.
Published in final edited form as: Coord Chem Rev. 2009;253(11-12):1649–1660. doi: 10.1016/j.ccr.2009.01.032

Figure 3.

Figure 3

The ubiquitin-proteasome pathway. A target protein degraded by the ubiquitin-proteasome pathway is first covalently modified by multiple ubiquitin (Ub) molecules in a three-stepped, highly regulated enzymatic process involving an Ub-activating (E1), Ub-conjugating (E2), and the Ub-ligating (E3) enzymes. The ubiquitinated protein is then escorted to the 26S proteasome, recognized by the 19S cap, de-ubiquitinated and then degraded by the catalytic 20S core into oligopeptides. The ubiquitin molecules are released and recycled.