Catalytic components of proteasomes and the regulation of proteinase activity

Rivett, A.Jennifer, Mason, Grant, Thomson, Stuart, Pike, Angela, Savory, Peter, & Murray, Rachael (1995) Catalytic components of proteasomes and the regulation of proteinase activity. Molecular Biology Reports, 25, pp. 35-41.

View at publisher


The proteasome (multicatalytic proteinase complex) is a large multimeric complex which is found in the nucleus and cytoplasm of eukaryotic cells. It plays a major role in both ubiquitin-dependent and ubiquitin-independent nonlysosomal pathways of protein degradation. Proteasome subunits are encoded by members of the same gene family and can be divided into two groups based on their similarity to the c~ and /3 subunits of the simpler proteasome isolated from Thermoplasma acidophilum. Proteasomes have a cylindrical structure composed of four rings of seven subunits. The 26S form of the proteasome, which is responsible for ubiquitin-dependent proteolysis, contains additional regulatory complexes. Eukaryotic proteasomes have multiple catalytic activities which are catalysed at distinct sites. Since proteasomes are unrelated to other known proteases, there are no clues as to which are the catalytic components from sequence alignments. It has been assumed from studies with yeast mutants that /3-type subunits play a catalytic role. Using a radiolabelled peptidyl chloromethane inhibitor of rat liver proteasomes we have directly identified RC7 as a catalytic component. Interestingly, mutants in Prel, the yeast homologue of RC7, have already been reported to have defective chymotrypsin-like activity. These results taken together confirm a direct catalytic role for these/3-type subunits. Proteasome activities are sensitive to conformational changes and there are several ways in which proteasome function may be modulated in vivo. Our recent studies have shown that in animal cells at least two proteasome subunits can undergo phosphorylation, the level of which is likely to be important for determining proteasome localization, activity or ability to form larger complexes. In addition, we have isolated two isoforms of the 26S proteinase.

Impact and interest:

17 citations in Scopus
20 citations in Web of Science®
Search Google Scholar™

Citation counts are sourced monthly from Scopus and Web of Science® citation databases.

These databases contain citations from different subsets of available publications and different time periods and thus the citation count from each is usually different. Some works are not in either database and no count is displayed. Scopus includes citations from articles published in 1996 onwards, and Web of Science® generally from 1980 onwards.

Citations counts from the Google Scholar™ indexing service can be viewed at the linked Google Scholar™ search.

ID Code: 50548
Item Type: Journal Article
Refereed: Yes
Keywords: catalytic subunits, multicatalytic proteinase, nonlysosomal proteolysis, phosphorylation
DOI: 10.1007/BF00990968
ISSN: 0301-4851
Subjects: Australian and New Zealand Standard Research Classification > BIOLOGICAL SCIENCES (060000) > BIOCHEMISTRY AND CELL BIOLOGY (060100) > Enzymes (060107)
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Deposited On: 23 May 2012 00:19
Last Modified: 15 Jul 2017 18:01

Export: EndNote | Dublin Core | BibTeX

Repository Staff Only: item control page