9IWR

26S proteasome trimer

This is a non-PDB format compatible entry.

Summary for 9IWR

• Entry DOI: 10.2210/pdb9iwr/pdb
• EMDB information: 60960
• Descriptor: Proteasome subunit beta type-1, Proteasome subunit alpha type-3, Proteasome subunit alpha type-4, ... (33 entities in total)
• Functional Keywords: proteasome, trimer, complex, psg, paracrystalline, hydrolase
• Biological source: Saccharomyces cerevisiae S288C; More
• Total number of polymer chains: 47
• Total formula weight: 1692659.85

Authors

Qu, L.,Tang, X.,Baumeister, W. (deposition date: 2024-07-25, release date: 2026-01-28, Last modification date: 2026-03-04)

Primary citation

Tang, X.,Qu, L.,Wilfling, F.,Beck, F.,Ernst, O.P.,Schulman, B.A.,Baumeister, W.,Enenkel, C.
Metabolically regulated proteasome supramolecular organization in situ.
Cell, 189:1153-1169.e16, 2026

PubMed Abstract: Many proteins localize in membraneless organelles. However, understanding the steps along membraneless organelle formation-and the structural impact on granule constituents-has been hindered by limited resolution of intracellular data. We address these challenges through in situ cryo-electron tomography (cryo-ET) along with formation of yeast proteasome storage granules (PSGs). During the transition from proliferation to quiescence, doubly capped 26S proteasomes arrested in an inactive state arrange into ∼7.5 MDa trimeric units, dispersed in the nucleoplasm and congregated along the nuclear envelope near the nuclear pore. 9-Å-resolution cryo-ET structures reveal that cytoplasmic PSGs formed in various energy-limiting conditions are paracrystalline arrays of bundled fibers, assembled from stacking of proteasome trimers. The paracrystalline arrangement maintains a pool of fully assembled inactive 26S proteasomes that are released in energy-rich conditions. Overall, our data reveal structural steps along the assembly of an intracellular membraneless organelle in situ and quinary structure formation controlling a major eukaryotic regulatory machine.

PubMed: 41605212
DOI: 10.1016/j.cell.2025.12.035

Experimental method

ELECTRON MICROSCOPY (9.1 Å)