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Yorodumi- PDB-22mm: Structure of human 26S proteasome complexed with midnolin(1-111+3... -
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Open data
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Basic information
| Entry | Database: PDB / ID: 22mm | |||||||||||||||||||||||||||
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| Title | Structure of human 26S proteasome complexed with midnolin(1-111+337-468) | |||||||||||||||||||||||||||
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Keywords | HYDROLASE / 26S proteasome / midnolin | |||||||||||||||||||||||||||
| Function / homology | Function and homology informationnegative regulation of glucokinase activity / thyrotropin-releasing hormone receptor binding / Impaired BRCA2 translocation to the nucleus / Impaired BRCA2 binding to SEM1 (DSS1) / nuclear proteasome complex / host-mediated perturbation of viral transcription / positive regulation of inclusion body assembly / integrator complex / proteasome accessory complex / meiosis I ...negative regulation of glucokinase activity / thyrotropin-releasing hormone receptor binding / Impaired BRCA2 translocation to the nucleus / Impaired BRCA2 binding to SEM1 (DSS1) / nuclear proteasome complex / host-mediated perturbation of viral transcription / positive regulation of inclusion body assembly / integrator complex / proteasome accessory complex / meiosis I / purine ribonucleoside triphosphate binding / proteasome regulatory particle / cytosolic proteasome complex / positive regulation of proteasomal protein catabolic process / proteasome-activating activity / Antigen processing: Ub, ATP-independent proteasomal degradation / proteasome regulatory particle, lid subcomplex / proteasome regulatory particle, base subcomplex / sperm glycocalyx / protein K63-linked deubiquitination / negative regulation of programmed cell death / metal-dependent deubiquitinase activity / Regulation of ornithine decarboxylase (ODC) / Proteasome assembly / proteasome core complex / perinuclear theca / Cross-presentation of soluble exogenous antigens (endosomes) / Somitogenesis / K63-linked deubiquitinase activity / transcription factor binding / Homologous DNA Pairing and Strand Exchange / Defective homologous recombination repair (HRR) due to BRCA1 loss of function / Defective HDR through Homologous Recombination Repair (HRR) due to PALB2 loss of BRCA1 binding function / Defective HDR through Homologous Recombination Repair (HRR) due to PALB2 loss of BRCA2/RAD51/RAD51C binding function / Resolution of D-loop Structures through Synthesis-Dependent Strand Annealing (SDSA) / Resolution of D-loop Structures through Holliday Junction Intermediates / proteasome binding / Impaired BRCA2 binding to RAD51 / myofibril / regulation of protein catabolic process / proteasome storage granule / proteasomal ubiquitin-independent protein catabolic process / sperm head-tail coupling apparatus / general transcription initiation factor binding / Presynaptic phase of homologous DNA pairing and strand exchange / blastocyst development / protein deubiquitination / immune system process / proteasome endopeptidase complex / NF-kappaB binding / proteasome core complex, beta-subunit complex / endopeptidase activator activity / threonine-type endopeptidase activity / proteasome assembly / mRNA export from nucleus / proteasome core complex, alpha-subunit complex / enzyme regulator activity / regulation of proteasomal protein catabolic process / inclusion body / TBP-class protein binding / : / ciliary tip / proteasome complex / bioluminescence / stem cell differentiation / Regulation of activated PAK-2p34 by proteasome mediated degradation / sarcomere / Autodegradation of Cdh1 by Cdh1:APC/C / APC/C:Cdc20 mediated degradation of Securin / generation of precursor metabolites and energy / ubiquitin binding / Asymmetric localization of PCP proteins / N-glycan trimming in the ER and Calnexin/Calreticulin cycle / Ubiquitin-dependent degradation of Cyclin D / SCF-beta-TrCP mediated degradation of Emi1 / NIK-->noncanonical NF-kB signaling / AUF1 (hnRNP D0) binds and destabilizes mRNA / TNFR2 non-canonical NF-kB pathway / centriole / sperm end piece / P-body / negative regulation of inflammatory response to antigenic stimulus / Assembly of the pre-replicative complex / Vpu mediated degradation of CD4 / Cdc20:Phospho-APC/C mediated degradation of Cyclin A / lipopolysaccharide binding / Dectin-1 mediated noncanonical NF-kB signaling / Degradation of DVL / Degradation of AXIN / Degradation of CRY and PER proteins / Hh mutants are degraded by ERAD / Activation of NF-kappaB in B cells / G2/M Checkpoints / Degradation of GLI1 by the proteasome / Hedgehog ligand biogenesis / Autodegradation of the E3 ubiquitin ligase COP1 / Regulation of RUNX3 expression and activity / Defective CFTR causes cystic fibrosis / GSK3B and BTRC:CUL1-mediated-degradation of NFE2L2 / Negative regulation of NOTCH4 signaling Similarity search - Function | |||||||||||||||||||||||||||
| Biological species | Homo sapiens (human)![]() synthetic construct (others) | |||||||||||||||||||||||||||
| Method | ELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 3.42 Å | |||||||||||||||||||||||||||
Authors | Liang, L. / Zhu, C. / Qin, L. | |||||||||||||||||||||||||||
| Funding support | China, 1items
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Citation | Journal: Nat Commun / Year: 2026Title: Structural dynamics of the midnolin-proteasome during ubiquitin-independent substrate turnover. Authors: Chuanda Zhu / Lu Qin / Zonglin Dai / Peng Zuo / Ao Yang / Lijun Zhong / Zhiqiang Lin / Ling Liang / ![]() Abstract: The 26S proteasome typically degrades proteins marked by ubiquitin chains. However, a distinct, ubiquitin-independent degradation pathway for nuclear proteins exists, mediated by the adaptor protein ...The 26S proteasome typically degrades proteins marked by ubiquitin chains. However, a distinct, ubiquitin-independent degradation pathway for nuclear proteins exists, mediated by the adaptor protein midnolin, yet its molecular mechanism remains poorly understood. Here, we present nine cryo-electron microscopy structures of the human 26S proteasome in complex with midnolin, which collectively delineate a near-complete catalytic cycle. Our structures reveal that midnolin binds to the proteasome via the RPN1 subunit by its C-terminal helix. Unexpectedly, its ubiquitin-like domain interacts with the RPN11 deubiquitinase in a non-catalytic role. This interaction positions the adjacent Catch domain, which is responsible for substrate binding, directly above the proteasomal entrance, potentially facilitating substrate entry into the proteasome. Furthermore, we observe four consecutive spiral staircase conformations of the AAA+ ATPase hexamer during substrate translocation. These findings provide insights into the mechanisms underlying ubiquitin-independent nuclear protein degradation and may help develop strategies for targeting nuclear proteins via direct proteasomal degradation. | |||||||||||||||||||||||||||
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Structure visualization
| Structure viewer | Molecule: Molmil Jmol/JSmol |
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Downloads & links
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Download
| PDBx/mmCIF format | 22mm.cif.gz | 2.5 MB | Display | PDBx/mmCIF format |
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| PDB format | pdb22mm.ent.gz | Display | PDB format | |
| PDBx/mmJSON format | 22mm.json.gz | Tree view | PDBx/mmJSON format | |
| Others | Other downloads |
-Validation report
| Arichive directory | https://data.pdbj.org/pub/pdb/validation_reports/2m/22mm ftp://data.pdbj.org/pub/pdb/validation_reports/2m/22mm | HTTPS FTP |
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-Related structure data
| Related structure data | ![]() 68472MC ![]() 9mboC ![]() 9mbpC ![]() 9mbqC ![]() 9u3lC ![]() 9u4mC ![]() 9u7rC ![]() 9w39C ![]() 9wbgC M: map data used to model this data C: citing same article ( |
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| Similar structure data | Similarity search - Function & homology F&H Search |
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Links
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Assembly
| Deposited unit | ![]()
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Components
-26S proteasome non-ATPase regulatory subunit ... , 10 types, 10 molecules UVWXYZacdu
| #1: Protein | Mass: 105958.234 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: Q99460 |
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| #2: Protein | Mass: 60935.297 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: O43242 |
| #3: Protein | Mass: 52979.359 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: O00232 |
| #4: Protein | Mass: 47526.688 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: O00231 |
| #5: Protein | Mass: 45592.285 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: Q15008 |
| #6: Protein | Mass: 37086.441 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P51665 |
| #7: Protein | Mass: 42995.359 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: Q9UNM6 |
| #8: Protein | Mass: 34488.824 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human)References: UniProt: O00487, Hydrolases; Acting on peptide bonds (peptidases); Omega peptidases |
| #9: Protein | Mass: 39536.676 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P48556 |
| #33: Protein | Mass: 100313.625 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: Q13200 |
-Protein , 4 types, 5 molecules eELlf
| #10: Protein | Mass: 8284.611 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P60896 | ||
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| #15: Protein | Mass: 45867.027 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: A0A087X2I1 | ||
| #22: Protein | Mass: 30150.277 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P25786#32: Protein | | Mass: 49195.016 Da / Num. of mol.: 1 Source method: isolated from a genetically manipulated source Details: Midnolin-mCherry, midnolin(1-111+337-468) Source: (gene. exp.) Homo sapiens (human), (gene. exp.) ![]() Gene: MIDN, mCherry / Production host: Homo sapiens (human) / References: UniProt: Q504T8, UniProt: A0A4D6FVK6 |
-26S proteasome regulatory subunit ... , 5 types, 5 molecules ABCDF
| #11: Protein | Mass: 48700.805 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P35998 |
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| #12: Protein | Mass: 49260.504 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P62191 |
| #13: Protein | Mass: 44852.121 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P62195 |
| #14: Protein | Mass: 47426.141 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P43686 |
| #16: Protein | Mass: 49266.457 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P17980 |
-Proteasome subunit alpha type- ... , 7 types, 12 molecules GgHhIiJKkMmj
| #17: Protein | Mass: 27301.262 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P60900#18: Protein | Mass: 25796.338 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P25787#19: Protein | Mass: 29394.648 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P25789#20: Protein | | Mass: 27929.891 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: O14818#21: Protein | Mass: 26435.977 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P28066#23: Protein | Mass: 28338.057 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P25788#31: Protein | | Mass: 27798.695 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: O14818 |
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-Proteasome subunit beta type- ... , 7 types, 14 molecules NnOoPpQqRrSsTt
| #24: Protein | Mass: 25246.455 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human)References: UniProt: P28072, proteasome endopeptidase complex #25: Protein | Mass: 29869.223 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human)References: UniProt: Q99436, proteasome endopeptidase complex #26: Protein | Mass: 22841.701 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P49720#27: Protein | Mass: 22864.277 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P49721#28: Protein | Mass: 28379.053 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human)References: UniProt: P28074, proteasome endopeptidase complex #29: Protein | Mass: 26391.201 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P20618#30: Protein | Mass: 29099.986 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P28070 |
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-Non-polymers , 5 types, 18 molecules 








| #34: Chemical | ChemComp-ZN / | ||||||
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| #35: Chemical | ChemComp-ATP / #36: Chemical | ChemComp-MG / #37: Chemical | #38: Chemical | ChemComp-LDZ / |
-Details
| Has ligand of interest | Y |
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| Has protein modification | Y |
-Experimental details
-Experiment
| Experiment | Method: ELECTRON MICROSCOPY |
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| EM experiment | Aggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction |
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Sample preparation
| Component | Name: 26S proteasome complexed with midnolin delCatch / Type: COMPLEX / Entity ID: #1-#33 / Source: NATURAL |
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| Source (natural) | Organism: Homo sapiens (human) |
| Buffer solution | pH: 7.4 |
| Specimen | Embedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES |
| Vitrification | Cryogen name: ETHANE |
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Electron microscopy imaging
| Experimental equipment | ![]() Model: Titan Krios / Image courtesy: FEI Company |
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| Microscopy | Model: TFS KRIOS |
| Electron gun | Electron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM |
| Electron lens | Mode: BRIGHT FIELD / Nominal defocus max: 1800 nm / Nominal defocus min: 800 nm |
| Image recording | Electron dose: 40 e/Å2 / Film or detector model: GATAN K3 BIOCONTINUUM (6k x 4k) |
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Processing
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| CTF correction | Type: PHASE FLIPPING AND AMPLITUDE CORRECTION | ||||||||||||||||||||||||
| 3D reconstruction | Resolution: 3.42 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 17418 / Symmetry type: POINT | ||||||||||||||||||||||||
| Refinement | Highest resolution: 3.42 Å Stereochemistry target values: REAL-SPACE (WEIGHTED MAP SUM AT ATOM CENTERS) | ||||||||||||||||||||||||
| Refine LS restraints |
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Homo sapiens (human)

China, 1items
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