{"uniprot":"A6NM45","gene":"CLDN24","name":"Putative claudin-24","organism":"Homo sapiens (Human)","status":"dark","length":220,"sequence":"MALIFRTAMQSVGLLLSLLGWILSIITTYLPHWKNLNLDLNEMENWTMGLWQTCVIQEEVGMQCKDFDSFLALPAELRVSRILMFLSNGLGFLGLLVSGFGLDCLRIGESQRDLKRRLLILGGILSWASGITALVPVSWVAHKTVQEFWDENVPDFVPRWEFGEALFLGWFAGLSLLLGGCLLNCAACSSHAPLALGHYAVAQMQTQCPYLEDGTADPQV","function_summary":"A multi-pass membrane component of epithelial tight junctions that assembles into linear strands to seal the paracellular space and organize cell polarity. It operates through multivalent binding to other junctional proteins and claudins, driving higher-order complex assembly that establishes and maintains the epithelial barrier at cell–cell contacts.","plain_language":"CLDN24 has barely been studied. The model's best guess: A multi-pass membrane component of epithelial tight junctions that assembles into linear strands to seal the paracellular space and organize cell polarity. It operates through multivalent binding to other junctional proteins and claudins, driving higher-order complex assembly that establishes and maintains the epithelial barrier at cell–cell contacts.","uniprot_summary":"Plays a major role in tight junction-specific functions.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0065003","label":"protein-containing complex assembly"}],"cellular_component":[{"id":"GO:0070160","label":"tight junction"}]},"interpro":[{"id":"IPR006187","name":"Claudin","type":"family","start":8,"end":190},{"id":"IPR004031","name":"PMP-22/EMP/MP20/Claudin","type":"family","start":12,"end":182},{"id":"IPR017974","name":"Claudin, conserved site","type":"conserved_site","start":49,"end":64}],"reasoning":"I begin with the InterPro architecture. The sequence is dominated by IPR006187 (Claudin family, residues 8–190), a hallmark of tight-junction strand-forming proteins. Nested within this, IPR004031 (PMP-22/EMP/MP20/Claudin family, residues 12–182) reinforces that the polypeptide belongs to the claudin/PMP-22 superfamily of four-pass membrane proteins that assemble into continuous tight-junction belts. Centrally, IPR017974 (Claudin, conserved site, residues 49–64) marks a conserved motif that stabilizes strand formation and paracellular barrier function. The ordered layout—an N-to-C four-helix membrane core with a conserved internal site—causes the protein to oligomerize laterally in the membrane and to form linear strands that define the epithelial tight junction.\n\nThis claudin architecture dictates the molecular function. Claudins lack classical catalytic motifs and instead operate through multivalent assembly and adhesion. The four-pass membrane scaffold and conserved site promote homo- and hetero-oligomerization with other claudins and junctional partners, which mechanistically requires multimeric contacts rather than enzymatic chemistry. This supports GO:0005515 protein binding as the operative molecular function: the protein binds other claudins, occludin, and scaffolding adaptors to build higher-order complexes.\n\nFrom this binding-driven assembly, the biological process follows. Tight junction strands nucleate and stabilize supramolecular assemblies that seal the apical–basal interface of epithelial sheets. The claudin core nucleates and extends linear polymers and meshworks, directly advancing GO:0065003 protein-containing complex assembly. By forming and maintaining these assemblies, the protein enforces the paracellular barrier and coordinates cell polarity cues.\n\nCellular location is implied by the same architecture. Claudins are classical multi-pass membrane constituents of tight junctions; the strand-forming topology and conserved site enforce tight junction targeting and retention. This places the protein at the cell–cell contact zone formalized as GO:0070160 tight junction, consistent with a junctional, membrane-embedded residency.\n\nMechanistically, I infer that the protein forms lateral oligomers via its claudin transmembrane bundle and conserved internal motif, generating continuous strands that seal the intercellular space. These strands recruit cytoplasmic scaffolds and signaling modules, tuning barrier strength and permeability. Likely interaction partners include other claudins for heterotypic strand formation, the MAGUK scaffold ZO-1 that anchors junctions, and membrane-associated glycoproteins such as occludin and JAMs. Together, these assemblies produce a stable, regulatable tight-junction barrier in epithelial tissues.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-A6NM45.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/A6NM45"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/A6NM45/entry","atlas":"/p/A6NM45"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}