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26S proteasome

Function: - multicatalytic proteinase complex - along with macro-autophagy, facilitates one of two major degradation pathways - 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]

Related

19S proteasome (PA700 complex) ubiquitin (UBCEP2, UBB, UBC)

General

macromolecular complex protease; proteinase; endopeptidase

Properties

MOTIF: active site MISC-INFO: SEDIMENTATION_COEFFICIENT 26 S

Database Correlations

Kegg map/map03050

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: 2226812
  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: 7896000
  3. Tidball J, 9th Annual UCLA Research Conference on Aging, June 17, 2004 (conference speaker)
  4. PROSITE :accession PS00674
  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: 15615647

Components

19S proteasome (PA700 complex) 20S proteasome MSS1 protein; 26S proteasome subunit 7 (PSMC2, MSS1) thyroid receptor-interacting protein 1; 26S proteasome regulatory subunit 8 (TRIP1, ATPase-5, PSMC5, SUG1)