{"uniprot":"Q1L5Z9","gene":"LONRF2","name":"LON peptidase N-terminal domain and RING finger protein 2","organism":"Homo sapiens (Human)","status":"dark","length":754,"sequence":"MSPEPVPPPPPPQCPGCDRAEPIAQRLEEGDEAFRAGDYEMAAELFRSMLAGLAQPDRGLCLRLGDALARAGRLPEALGAFRGAARLGALRPEELEELAGGLVRAVGLRDRPLSAENPGGEPEAPGEGGPAPEPRAPRDLLGCPRCRRLLHKPVTLPCGLTVCKRCVEPGPARPQVRRVNVVLSGLLEKCFPAECRLRRLAGQARSLQRQQQPEAALLRCDQALELAPDDNSLLLLRAELYLTMKNYEQALQDASAACQNEPLLIKGHQVKAQALSGLGRSKEVLKEFLYCLALNPECNSVKKEAQKVMCEVLFSATANVHENLTSSIQSRLKAQGHSHMNAQALLEEGDAGSSENSSEKSDMLGNTNSSVLYFILGLHFEEDKKALESILPTAPSAGLKRQFPDDVEDAPDLNAPGKIPKKDLSLQRSPNSETEESQGLSLDVTDFECALCMRLLFEPVTTPCGHTFCLKCLERCLDHAPHCPLCKDKLSELLASRNFNITVLAEELIFRYLPDELSDRKRIYDEEMSELSNLTRDVPIFVCAMAFPTVPCPLHVFEPRYRLMIRRCMETGTKRFGMCLSAEHAGLSEYGCMLEIKDVRTFPDGSSVVDAIGISRFRVLSHRHRDGYNTADIEYLEDEKVEGPEYEELAALHDSVHQQSVSWFASLQDRMKEQILSHFGVMPDREPEPQSNPSGPAWSWWILAVLPLERKAQLAILGMTSLKERLLAIRRILVIITRKMNSRQELANARERNN","function_summary":"A nuclear scaffold that organizes ubiquitination and proteasome-directed protein turnover. Its N-terminal helical solenoid and internal repeats create a multivalent platform that captures client proteins and assembly factors, while two RING modules catalyze and regulate ubiquitin transfer and autoubiquitination. A C-terminal Lon protease–related and PUA-like platform stabilizes higher-order assemblies and substrate engagement. Together these modules concentrate ubiquitination machinery in the nucleus, promote substrate ubiquitination, and enhance proteasome-dependent degradation pathways.","plain_language":"LONRF2 has barely been studied. The model's best guess: A nuclear scaffold that organizes ubiquitination and proteasome-directed protein turnover. Its N-terminal helical solenoid and internal repeats create a multivalent platform that captures client proteins and assembly factors, while two RING modules catalyze and regulate ubiquitin transfer and autoubiquitination.","uniprot_summary":"May be involved in ubiquitination and proteasome-mediated degradation.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0032436","label":"positive regulation of proteasomal ubiquitin-dependent protein catabolic process"},{"id":"GO:0016567","label":"protein ubiquitination"},{"id":"GO:0051865","label":"protein autoubiquitination"}],"cellular_component":[{"id":"GO:0005634","label":"nucleus"}]},"interpro":[{"id":"IPR011990","name":"Tetratricopeptide-like helical domain superfamily","type":"homologous_superfamily","start":19,"end":102},{"id":"IPR013083","name":"Zinc finger, RING/FYVE/PHD-type","type":"homologous_superfamily","start":134,"end":194},{"id":"IPR011990","name":"Tetratricopeptide-like helical domain superfamily","type":"homologous_superfamily","start":195,"end":311},{"id":"IPR013083","name":"Zinc finger, RING/FYVE/PHD-type","type":"homologous_superfamily","start":415,"end":518},{"id":"IPR046336","name":"Lon protease, N-terminal domain superfamily","type":"homologous_superfamily","start":519,"end":636},{"id":"IPR015947","name":"PUA-like superfamily","type":"homologous_superfamily","start":537,"end":733},{"id":"IPR001841","name":"Zinc finger, RING-type","type":"domain","start":143,"end":193},{"id":"IPR001841","name":"Zinc finger, RING-type","type":"domain","start":448,"end":487},{"id":"IPR003111","name":"Lon protease, N-terminal domain","type":"domain","start":528,"end":737},{"id":"IPR019734","name":"Tetratricopeptide repeat","type":"repeat","start":197,"end":230},{"id":"IPR019734","name":"Tetratricopeptide repeat","type":"repeat","start":231,"end":264},{"id":"IPR019734","name":"Tetratricopeptide repeat","type":"repeat","start":265,"end":298},{"id":"IPR017907","name":"Zinc finger, RING-type, conserved site","type":"conserved_site","start":464,"end":473}],"reasoning":"I begin by dissecting the domain architecture. The N-terminus carries IPR011990 (Tetratricopeptide-like helical domain superfamily, residues 19–102), followed by a second helical scaffold IPR011990 segment (residues 195–311). Within this N-terminal-to-mid region, there is a defined TPR array: IPR019734 repeat units occur consecutively at residues 197–230, 231–264, and 265–298. TPR-like solenoids create extended protein–protein interaction surfaces that recruit client proteins and assembly factors; this architecture causes multivalent protein binding and scaffolding, supporting GO:0005515 protein binding as a core molecular function.\n\nImmediately downstream, two RING-type zinc-finger modules are present. The first is a canonical RING region: IPR001841 (Zinc finger, RING-type, residues 143–193) embedded within IPR013083 (Zinc finger, RING/FYVE/PHD-type superfamily, residues 134–194). A second RING module appears later: IPR001841 (Zinc finger, RING-type, residues 448–487) within IPR013083 (residues 415–518), with a conserved site IPR017907 (Zinc finger, RING-type, conserved site, residues 464–473). RING domains catalyze ubiquitin transfer by coordinating E2~Ub thioesters and positioning substrates; thus, this dual RING layout equips the protein both to assemble ubiquitination machinery and to undergo GO:0051865 protein autoubiquitination. The presence of two RING modules suggests either sequential E2 engagements or auto-regulatory ubiquitin tagging that tunes activity and localization.\n\nThe C-terminal half transitions into an Lon protease–related scaffold: IPR046336 (Lon protease, N-terminal domain superfamily, residues 519–636) and IPR003111 (Lon protease, N-terminal domain, residues 528–737), accompanied by IPR015947 (PUA-like superfamily, residues 537–733). Lon N-terminal and PUA-like folds form β-barrel/α-solenoid assemblies that bind RNA and acidic/basic patches on client proteins; in this context they function as an oligomerization and substrate-handling platform rather than a catalytic protease. Together with the N-terminal TPR array, this creates a bipartite solenoidal chassis that captures, organizes, and hands off substrates to ubiquitin machinery.\n\nFrom these features, the molecular function resolves as multivalent protein binding (GO:0005515) with embedded ubiquitin-transfer capacity via RING fingers. The biological process follows causally: the TPR and Lon-like scaffolds concentrate substrates and E3/E2 components, while the RING modules drive ubiquitin attachment, establishing GO:0016567 protein ubiquitination. The same architecture explains GO:0032436 positive regulation of proteasomal ubiquitin-dependent protein catabolic process: by scaffolding E2/E3 modules and funneling ubiquitinated clients toward the proteasome, the protein enhances proteasomal flux. Autoubiquitination (GO:0051865) emerges naturally from the dual RING arrangement and provides a feedback mechanism for turnover and trafficking.\n\nCellular location is inferred from function and architecture. The absence of transmembrane segments and the presence of nuclear-associated scaffolding argue for a soluble nuclear role. The stated nuclear enrichment aligns with assembly of ubiquitination hubs that regulate chromatin-associated and transcriptional substrates; thus the cellular component is the GO:0005634 nucleus.\n\nMechanistically, the protein operates as a nuclear E3-scaffold. The N-terminal TPR solenoid recruits client proteins and adaptors; the first RING domain nucleates ubiquitin transfer; the C-terminal Lon/PUA-like platform stabilizes higher-order assemblies and substrate engagement; the second RING module modulates activity and supports autoubiquitination. This architecture causes efficient substrate capture and handoff to E2/E3 partners, thereby promoting proteasome-directed degradation. Likely interaction partners include nuclear E2 conjugating enzymes and E3s that cooperate with RING scaffolds, as well as proteasome receptors and RNA-associated factors that localize substrates in the nucleus. I therefore hypothesize transient complexes with ubiquitin-conjugating enzymes and nuclear proteostasis hubs that together tune ubiquitin signaling and proteasomal throughput.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q1L5Z9.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q1L5Z9"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q1L5Z9/entry","atlas":"/p/Q1L5Z9"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}