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| Title | Structures of dynamic interactors at native proteasomes by PhIX-MS and cryo-electron microscopy. |
|---|---|
| Journal, issue, pages | Mol Cell, Vol. 86, Issue 15, Page 3067-3085.e13, Year 2026 |
| Publish date | Aug 6, 2026 |
Authors | Kitaik Lee / Hitendra Negi / Xiang Chen / Katerina Atallah-Yunes / Sophia Truslow / Rithik E Castelino / Mary R Guest / Anthony M Ciancone / Xiuxiu Lu / Sergey G Tarasov / Raj Chari / Kylie J Walters / Francis J O'Reilly / ![]() |
| PubMed Abstract | Molecular machines rely on dynamic, low-affinity interactions to perform their functional roles. We developed PhIX-MS (photo-induced in situ crosslinking-mass spectrometry), a structural proteomics ...Molecular machines rely on dynamic, low-affinity interactions to perform their functional roles. We developed PhIX-MS (photo-induced in situ crosslinking-mass spectrometry), a structural proteomics workflow to capture topological information for such transient interactions in cells by UV-activated crosslinking. Applying PhIX-MS with cryo-electron microscopy (cryo-EM) to proteasomes, we mapped the redox sensor TXNL1 at the proteasome regulatory particle (RP), including its dynamic thioredoxin-like domain near RPN2/PSMD1 and RPN13/ADRM1, where it is ideal for reducing substrates prior to proteolysis. RPs without the proteolytic core particle (CP) were structurally resolved while bound to TXNL1 and/or the chaperone PSMD5/S5b, which inserts its C terminus into the ATPase pore, causing extensive structural rearrangements. Additionally, PhIX-MS and AlphaFold identified the ubiquitin ligase UBE3C/Hul5 at RPN2, RPN3, and a dynamic RPN10 region, tethering UBE3C above the substrate entry channel. Our integrative approach enables the localization of native, low-affinity protein interactions and is broadly applicable to dynamic macromolecular assemblies. |
External links | Mol Cell / PubMed:42476128 |
| Methods | EM (single particle) |
| Resolution | 3.02 - 5.35 Å |
| Structure data | EMDB-71737, PDB-9pmj: EMDB-71740, PDB-9pmo: EMDB-71741, PDB-9pmq: ![]() EMDB-71791: Human 19S proteasome regulatory particle (RP) without observing TXNL1 PITH domain bound ![]() EMDB-71795: Human 19S proteasome regulatory particle (RP) without observing TXNL1 PITH domain bound but with extra density adjacent to RPT1/RPT2 EMDB-71810, PDB-9pro: EMDB-71813, PDB-9prt: EMDB-76283, PDB-12bm: ![]() EMDB-76415: Human 19S proteasome regulatory particle bound to TXNL1 PITH domain and p28 |
| Chemicals | ![]() ChemComp-ADP: ![]() ChemComp-AGS: ![]() ChemComp-MG: ![]() ChemComp-ZN: |
| Source |
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Keywords | HYDROLASE / Proteasome / 19S / RP / TXNL1 / 26S / PSMD5 |
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homo sapiens (human)
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