Conformational Landscape of the p28-Bound Human Proteasome Regulatory Particle.
|Title||Conformational Landscape of the p28-Bound Human Proteasome Regulatory Particle.|
|Publication Type||Journal Article|
|Year of Publication||2017|
|Authors||Lu Y, Wu J, Dong Y, Chen S, Sun S, Ma Y-B, Ouyang Q, Finley D, Kirschner MW, Mao Y|
|Date Published||2017 Jul 20|
The proteasome holoenzyme is activated by its regulatory particle (RP) consisting of two subcomplexes, the lid and the base. A key event in base assembly is the formation of a heterohexameric ring of AAA-ATPases, which is guided by at least four RP assembly chaperones in mammals: PAAF1, p28/gankyrin, p27/PSMD9, and S5b. Using cryogenic electron microscopy, we analyzed the non-AAA structure of the p28-bound human RP at 4.5 Å resolution and determined seven distinct conformations of the Rpn1-p28-AAA subcomplex within the p28-bound RP at subnanometer resolutions. Remarkably, the p28-bound AAA ring does not form a channel in the free RP and spontaneously samples multiple "open" and "closed" topologies at the Rpt2-Rpt6 and Rpt3-Rpt4 interfaces. Our analysis suggests that p28 assists the proteolytic core particle to select a specific conformation of the ATPase ring for RP engagement and is released in a shoehorn-like fashion in the last step of the chaperone-mediated proteasome assembly.
|Alternate Journal||Mol. Cell|