{"uniprot":"Q8TBF2","gene":"PRXL2B","name":"Prostamide/prostaglandin F synthase","organism":"Homo sapiens (Human)","status":"dark","length":198,"sequence":"MSTVDLARVGACILKHAVTGEAVELRSLWREHACVVAGLRRFGCVVCRWIAQDLSSLAGLLDQHGVRLVGVGPEALGLQEFLDGDYFAGELYLDESKQLYKELGFKRYNSLSILPAALGKPVRDVAAKAKAVGIQGNLSGDLLQSGGLLVVSKGGDKVLLHFVQKSPGDYVPKEHILQVLGISAEVCASDPPQCDREV","function_summary":"A soluble human redox-scaffold that uses a thioredoxin-like core within a peroxiredoxin-like framework to bind partner proteins and organize pathways that produce prostaglandins and govern their secretion. By assembling and tuning redox-sensitive complexes, it supports prostaglandin biosynthesis and can be packaged into extracellular vesicles, positioning it to influence secretion both inside cells and via exosome-mediated export.","plain_language":"PRXL2B has barely been studied. The model's best guess: A soluble human redox-scaffold that uses a thioredoxin-like core within a peroxiredoxin-like framework to bind partner proteins and organize pathways that produce prostaglandins and govern their secretion. By assembling and tuning redox-sensitive complexes, it supports prostaglandin biosynthesis and can be packaged into extracellular vesicles, positioning it to influence secretion both inside cells and via exosome-mediated export.","uniprot_summary":"Involved in prostaglandin biosynthesis and secretion.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0001516","label":"prostaglandin biosynthetic process"}],"cellular_component":[{"id":"GO:0070062","label":"extracellular exosome"}]},"interpro":[{"id":"IPR036249","name":"Thioredoxin-like superfamily","type":"homologous_superfamily","start":17,"end":110},{"id":"IPR032801","name":"Peroxiredoxin-like 2A/B/C","type":"family","start":20,"end":179}],"reasoning":"I begin with the InterPro architecture. The N-terminal core from residues 17–110 matches IPR036249 (Thioredoxin-like superfamily, homologous_superfamily), establishing a canonical thioredoxin fold that supports reversible thiol chemistry. This core is embedded within a larger peroxiredoxin scaffold: residues 20–179 align with IPR032801 (Peroxiredoxin-like 2A/B/C family), which specifies the Prx2A/2B/2C lineage. This ordered layout—an N-terminal thioredoxin-like catalytic platform extended by a peroxiredoxin-like family envelope—creates a redox-active module that typically binds partner proteins and cycles cysteine-based chemistry. Such thioredoxin-fold assemblies commonly function as adaptable interaction hubs rather than obligate enzymes, which causally supports GO:0005515 protein binding as the operative molecular function.\n\nFrom this fold, I infer how the protein influences lipid pathways. Peroxiredoxin-like scaffolds often tune redox-sensitive nodes that gate eicosanoid production. The Prx-like 2A/B/C family is well-suited to modulate cysteine-centered switches that control prostaglandin synthesis and secretion. This architecture therefore provides a mechanistic route into GO:0001516 prostaglandin biosynthetic process: by stabilizing or assembling complexes that channel arachidonic acid through cyclooxygenase and downstream pathways, the protein can bias prostaglandin output and release.\n\nCellular placement follows from both the soluble thioredoxin-like core and the absence of transmembrane features, pointing to a soluble pool that can be packaged into extracellular vesicles. The explicit evidence for vesicular export aligns with GO:0070062 extracellular exosome. A soluble redox-scaffold that traffics via exosomes can act at the cell surface or in the extracellular milieu to regulate prostaglandin secretion, while its intracellular pool organizes assembly and signaling.\n\nPutting these elements together, I propose a mechanism in which the thioredoxin-like/peroxiredoxin-like architecture forms a redox-tunable scaffold that binds partner proteins (GO:0005515), assembles prostaglandin-synthesis machinery (GO:0001516), and is exported in extracellular exosomes (GO:0070062) to modulate secretion. Likely interaction partners include enzymes and adaptors of the prostaglandin pathway and vesicle biogenesis machinery. I hypothesize transient complexes with cyclooxygenases and their accessory factors to steer pathway flux, and with ESCRT or tetraspanin systems to enable exosome loading and delivery of prostaglandins and associated cargo.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q8TBF2.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q8TBF2"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q8TBF2/entry","atlas":"/p/Q8TBF2"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}