{"uniprot":"Q8IX19","gene":"MCEMP1","name":"Mast cell-expressed membrane protein 1","organism":"Homo sapiens (Human)","status":"dark","length":187,"sequence":"MEVEEIYKHQEVKMQAPAFRDKKQGVSAKNQGAHDPDYENITLAFKNQDHAKGGHSRPTSQVPAQCRPPSDSTQVPCWLYRAILSLYILLALAFVLCIILSAFIMVKNAEMSKELLGFKRELWNVSNSVQACEERQKRGWDSVQQSITMVRSKIDRLETTLAGIKNIDTKVQKILEVLQKMPQSSPQ","function_summary":"A mast cell-enriched single-pass membrane protein that oligomerizes to organize signaling assemblies at the cell surface and within secretory granule membranes. By cycling between these compartments, it promotes assembly of membrane-proximal complexes that potentiate ERK pathway signaling and couple granule-dependent exocytosis to surface receptor pathways, thereby tuning mast cell activation and secretory responses.","plain_language":"MCEMP1 has barely been studied. The model's best guess: A mast cell-enriched single-pass membrane protein that oligomerizes to organize signaling assemblies at the cell surface and within secretory granule membranes. By cycling between these compartments, it promotes assembly of membrane-proximal complexes that potentiate ERK pathway signaling and couple granule-dependent exocytosis to surface receptor pathways, thereby tuning mast cell activation and secretory responses.","uniprot_summary":"Mast cell-expressed membrane protein.","go_terms":{"molecular_function":[{"id":"GO:0042802","label":"identical protein binding"}],"biological_process":[{"id":"GO:0070374","label":"positive regulation of ERK1 and ERK2 cascade"}],"cellular_component":[{"id":"GO:0005886","label":"plasma membrane"},{"id":"GO:0070821","label":"tertiary granule membrane"},{"id":"GO:0035579","label":"specific granule membrane"}]},"interpro":[{"id":"IPR038818","name":"Mast cell-expressed membrane protein 1","type":"family","start":1,"end":186}],"reasoning":"I begin with the InterPro architecture: IPR038818 (Mast cell-expressed membrane protein 1 family) spans residues 1–186 and covers the entire polypeptide, indicating a compact, lineage-specific membrane protein family rather than a modular enzyme. The full-length family signature without catalytic motifs points to a non-enzymatic role, typically scaffolding or adhesion-like functions. The annotation as a single-pass type I membrane protein implies an N-terminal luminal/extracellular ectodomain and a short C-terminal cytosolic tail. This topology is well-suited for organizing membrane-proximal signaling assemblies and for homotypic clustering.\n\nFrom this architecture, the most direct molecular function is mediated by self-association. The presence of GO:0042802 identical protein binding is mechanistically consistent with a type I single-pass membrane protein that forms homodimers or higher-order oligomers to nucleate signaling platforms. Such self-association provides avidity and spatial control over downstream pathways.\n\nThis oligomerizing membrane scaffold naturally feeds into MAPK pathway control. The explicit linkage to GO:0070374 positive regulation of ERK1 and ERK2 cascade follows causally: a membrane-tethered oligomer can recruit or stabilize upstream components (e.g., adaptor proteins and small GTPases) that funnel signals into ERK1/2. The luminal ectodomain can sense or organize extracellular/secretory-granule cues, while the cytosolic tail concentrates Ras–Raf–MEK–ERK assembly points, thereby elevating ERK pathway throughput.\n\nCellular localization is bifurcated between the cell surface and secretory organelles. The GO cellular component set includes GO:0005886 plasma membrane and granule membranes—GO:0070821 tertiary granule membrane and GO:0035579 specific granule membrane—matching a trafficking itinerary characteristic of mast cell exocytosis. A single-pass type I topology and granule residency together indicate that the protein cycles between storage granules and the plasma membrane. This itinerary explains how it couples granule-derived signals to surface receptor pathways and tunes ERK activation in response to degranulation cues.\n\nIntegrating these lines of evidence yields a mechanistic hypothesis: the protein forms homodimers/oligomers (identical protein binding) that concentrate and stabilize ERK-activating assemblies at the plasma membrane and within mast cell granule membranes. By cycling between these compartments, it coordinates receptor-proximal signaling with vesicle-mediated outputs that culminate in ERK1/2 pathway upregulation. Likely interaction partners include homotypic MEMP-1 assemblies; membrane-proximal adaptors (e.g., SH2/SH3-containing scaffolds), small GTPases that seed Ras–ERK signaling, and trafficking machinery that governs mast cell granule exocytosis. This arrangement causally links its membrane-anchored oligomerization to ERK cascade potentiation and to the specialized biology of mast cells.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q8IX19.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q8IX19"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q8IX19/entry","atlas":"/p/Q8IX19"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}