2026-01-28 マックス・プランク研究所
Seeing the invisible: Cryoelectron tomography reveals how proteasomes organize inside yeast cells into paracrystalline structures. Close-up view shows three proteasomes binding together to form a trimer – the basic building block of proteasome storage granules, never before observed in cells. © MPI of Biochemistry/ Xiaomeng Tang, Lu Qu
<関連情報>
- https://www.mpg.de/26065782/structure-and-function-of-proteasome-storage-granules-elucidated
- https://www.cell.com/cell/fulltext/S0092-8674(25)01485-0
代謝制御されたプロテアソーム超分子のin situ組織化 Metabolically regulated proteasome supramolecular organization in situ
Xiaomeng Tang ∙ Lu Qu ∙ Florian Wilfling ∙ … ∙ Brenda A. Schulman ∙ Wolfgang Baumeister ∙ Cordula Enenkel
Cell Published:January 27, 2026
DOI:https://doi.org/10.1016/j.cell.2025.12.035
Highlights
- In situ structural progression to a membraneless organelle formed upon nutrient depletion
- Inactive yeast 26S proteasome monomers oligomerize into trimers at low metabolic activity
- Proteasome trimers form paracrystalline arrays in proteasome storage granules (PSGs)
- Higher-order structures rationalize the material properties and regulatory functions of PSGs
Summary
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.
