EMD-25848

Single-particle
2.97 Å
EMD-25848 Deposition: 05/01/2022
Map released: 10/08/2022
Last modified: 28/02/2024
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links

EMD-25848

Cryo-EM structure of the 20S Alpha 3 Deletion proteasome core particle in complex with FUB1

EMD-25848

Single-particle
2.97 Å
EMD-25848 Deposition: 05/01/2022
Map released: 10/08/2022
Last modified: 28/02/2024
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Sample Organism: Saccharomyces cerevisiae S288C
Sample: 20S proteasome from alpha3delta proteasome mutant in complex with Silencing boundary-establishment protein FUB1
Fitted models: 7teo (Avg. Q-score: 0.532)

Deposition Authors: Walsh Jr RM , Rawson S
Yeast PI31 inhibits the proteasome by a direct multisite mechanism.
Rawson S , Walsh Jr RM , Velez B , Schnell HM , Jiao F, Blickling M, Ang J, Bhanu MK, Huang L , Hanna J
(2022) Nat Struct Mol Biol , 29 , 791 - 800
PUBMED: 35927584
DOI: doi:10.1038/s41594-022-00808-5
ISSN: 1545-9985
Abstract:
Proteasome inhibitors are widely used as therapeutics and research tools, and typically target one of the three active sites, each present twice in the proteasome complex. An endogeneous proteasome inhibitor, PI31, was identified 30 years ago, but its inhibitory mechanism has remained unclear. Here, we identify the mechanism of Saccharomyces cerevisiae PI31, also known as Fub1. Using cryo-electron microscopy (cryo-EM), we show that the conserved carboxy-terminal domain of Fub1 is present inside the proteasome's barrel-shaped core particle (CP), where it simultaneously interacts with all six active sites. Targeted mutations of Fub1 disrupt proteasome inhibition at one active site, while leaving the other sites unaffected. Fub1 itself evades degradation through distinct mechanisms at each active site. The gate that allows substrates to access the CP is constitutively closed, and Fub1 is enriched in mutant CPs with an abnormally open gate, suggesting that Fub1 may function to neutralize aberrant proteasomes, thereby ensuring the fidelity of proteasome-mediated protein degradation.