ATP hydrolysis is required for degradation of polyubiquitinated proteins by the 26S proteasome but is thought to play no role in proteasomal stability during the catalytic cycle. In contrast to this view, we report that ATP hydrolysis triggers rapid dissociation of the 19S regulatory particles from immunopurified 26S complexes in a manner coincident with release of the bulk of proteasome-interacting proteins. Strikingly, this mechanism leads to quantitative disassembly of the 19S into subcomplexes and free Rpn10, the polyubiquitin binding subunit. Biochemical reconstitution with purified Sic1, a prototype substrate of the Cdc34/SCF ubiquitin ligase, suggests that substrate degradation is essential for triggering the ATP hydrolysis-dependent dissociation and disassembly of the 19S and that this mechanism leads to release of degradation products. This is the first demonstration that a controlled dissociation of the 19S regulatory particles from the 26S proteasome is part of the mechanism of protein degradation.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to SciCrunch, however this is not currently a free service.