The 26S proteasome: ubiquitin-mediated proteolysis in the tunnel.
The 26S proteasome is a self-compartmentalizing protease responsible for the degradation of intracellular proteins. This giant intracellular protease is formed by several subunits arranged into two 19S polar caps-where protein recognition and ATP-dependent unfolding occur-flanking a 20S central barrel-shaped structure with an inner proteolytic chamber. Proteins targeted to the 26S proteasome are conjugated with a polyubiquitin chain by an enzymatic cascade before delivery to the 26S proteasome for degradation into oligopeptides. As a self-compartmentalizing protease, the 26S proteasome circumvents proteins not destined for degradation and can be deployed to the cytoplasmic and nuclear compartments. The 26S proteasome is a representative of emerging group of giant proteases, including tricorn protease, multicorn protease, and TPPII (tripeptidyl peptidase II).
Kierszenbaum
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Department of Cell Biology and Anatomical Sciences, The City University of New York Medical School, New York, NY 10031, USA. kier@med.cuny.edu
D000818:Animals; D002451:Cell Compartmentation; D006801:Humans; D008297:Male; D010447:Peptide Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D013091:Spermatogenesis; D014452:Ubiquitins / Q000378:metabolism*
D014452:Ubiquitins; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease