26s Proteasome

From Anvita Health Wiki

Contents 1 Function 2 Structure 3 More General Terms 4 Additional Terms 5 Internet Database 6 References

Function

• multicatalytic proteinase complex
• has an ATP-dependent proteolytic activity
• cleavage of peptide bonds with very broad specificity
• cleaves peptides with Arg, Phe, Tyr, Leu, & Glu adjacent to the leaving group at neutral or slightly basic pH
• tyrosine phosphorylation of specific subunits of proteasomes may enhance translocation into the nucleus
• the proteasome is refered to as an organelle involved in ubiquitin-mediated degradation of proteins [2]
• the ubiquitin-proteasome system is NOT able to breakdown muscle fibril proteins. [2]

Structure

• composed of at least 15 non identical subunits which form a highly ordered ring-shaped structure
• two 19S regulatory caps at the end of the 20S proteasome barrel form the 26S proteasome. [5]
• the 19S caps mediate recognition of polyubiquitin & unfold the target protein for degradation
• the unfolded protein is fed into the 20S proteasome chamber for proteolysis. [5]

More General Terms

• macromolecular complex
• protease; proteinase; endopeptidase

Additional Terms

• 19S proteasome (PA700 complex)
• ubiquitin (RPS27A, UBA80, UBCEP1, UBA52, UBCEP2, UBB, UBC)

Internet Database

Prosite: [1]
Kegg: [2]

References

1. Tanaka K, Yoshimura T, Tamura T, Fujiwara T, Kumatori A, Ichihara A. Possible mechanism of nuclear translocation of proteasomes. FEBS Lett. 1990 Oct 1;271(1-2):41-6. Review. PMID: [3]
2. Allende JE, Allende CC. Protein kinases. 4. Protein kinase CK2: an enzyme with multiple substrates and a puzzling regulation. FASEB J. 1995 Mar;9(5):313-23. Review. PMID: [4]
3. Tidball J, 9th Annual UCLA Research Conference on Aging, June 17, 2004 (conference speaker)
4. PROSITE [5]
5. Kosik KS, Shimura H. Phosphorylated tau and the neurodegenerative foldopathies. Biochim Biophys Acta. 2005 Jan 3;1739(2-3):298-310. Epub 2004 Nov 26. Review. PMID: [6]

26S proteasome