9pf1

Nub1/Fat10-processing human 26S proteasome with Rpt4 at top of spiral staircase (AAA+ motor locally refined)

spinqualitylabelsall models 9pf1, resolution 3.57Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 9pf1 is a 10 chain structure with sequence from Homo sapiens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 3.57Å Ligands: ADP, ATP, MG, ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function PRS7_HUMAN The 26S protease is involved in the ATP-dependent degradation of ubiquitinated proteins. The regulatory (or ATPase) complex confers ATP dependency and substrate specificity to the 26S complex. In case of HIV-1 infection, positive modulator of Tat-mediated transactivation. Publication Abstract from PubMed The 26S proteasome targets many cellular proteins for degradation during homeostasis and quality control. Proteasome-interacting cofactors modulate these functions and aid in substrate degradation. Here we solve high-resolution structures of the redox active cofactor TXNL1 bound to the human 26S proteasome at saturating and substoichiometric concentrations by time-resolved cryo-electron microscopy (cryo-EM). We identify distinct binding modes of TXNL1 that depend on the proteasome conformation and ATPase motor states. Together with biophysical and biochemical experiments, we show that the resting-state proteasome binds TXNL1 with low affinity and in variable positions on top of the Rpn11 deubiquitinase. In contrast, in the actively degrading proteasome, TXNL1 uses additional interactions for high-affinity binding, whereby its C-terminal tail covers the catalytic groove of Rpn11 and coordinates the active-site Zn(2+). Furthermore, these cryo-EM structures of the degrading proteasome capture the ATPase hexamer in several spiral-staircase arrangements that indicate temporally asymmetric hydrolysis and conformational changes in bursts during mechanical substrate unfolding and translocation. Remarkably, we catch the proteasome in the act of unfolding the beta-barrel mEos3.2 substrate while the ATPase hexamer is in a particular staircase register. Our findings advance current models for protein translocation through hexameric AAA+ motors and reveal how the proteasome uses its distinct conformational states to coordinate cofactor binding and substrate processing. Structural landscape of the degrading 26S proteasome reveals conformation-specific binding of TXNL1.,Arkinson C, Gee CL, Zhang Z, Dong KC, Martin A Nat Struct Mol Biol. 2025 Nov 6. doi: 10.1038/s41594-025-01695-2. PMID:41198955 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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