IgG receptor FcRn large subunit p51 (FCGRT) is a 365-residue protein from Homo sapiens. This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: P55899.
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The mean pLDDT of this model is 85.0 (confident overall). pLDDT is AlphaFold's per-residue confidence score from 0 to 100. In MolViewer, choose the B-factor color scheme to color the model by pLDDT, because AlphaFold stores it in the B-factor column.
| pLDDT band | Meaning | Share of residues |
|---|---|---|
| Above 90 | Very high: backbone and side chains are usually accurate | 72% |
| 70 to 90 | Confident: backbone generally right | 9% |
| 50 to 70 | Low: treat with caution | 5% |
| Below 50 | Very low: often disordered regions | 14% |
What pLDDT means and how to read it
Cell surface receptor that transfers passive humoral immunity from the mother to the newborn. Binds to the Fc region of monomeric immunoglobulin gamma and mediates its selective uptake from milk (PubMed:10933786, PubMed:7964511). IgG in the milk is bound at the apical surface of the intestinal epithelium. The resultant FcRn-IgG complexes are transcytosed across the intestinal epithelium and IgG is released from FcRn into blood or tissue fluids. Throughout life, contributes to effective humoral immunity by recycling IgG and extending its half-life in the circulation. Mechanistically, monomeric IgG binding to FcRn in acidic endosomes of endothelial and hematopoietic cells recycles IgG to the…
FcRn complex consists of two subunits: p51, and p14 which is equivalent to beta-2-microglobulin. It forms an MHC class I-like heterodimer (By similarity). Interacts with albumin/ALB; this interaction regulates ALB homeostasis (PubMed:24469444, PubMed:28330995)
Cell membrane, Endosome membrane
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 6C98 | X-ray | 1.85 Å | A/C=24-297 |
| 6QIO | X-ray | 1.95 Å | B=24-297 |
| 6C97 | X-ray | 2.0 Å | A/C=24-297 |
| 6C99 | X-ray | 2.0 Å | A/C=24-297 |
| 6NHA | X-ray | 2.38 Å | A=24-296 |
| 6LA6 | EM | 2.39 Å | E=28-290 |
| 4K71 | X-ray | 2.4 Å | B/E=24-297 |
| 6WNA | X-ray | 2.4 Å | A=27-290 |
| 9MI6 | X-ray | 2.41 Å | A=24-297 |
| 6QIP | X-ray | 2.45 Å | B=24-297 |
| 6WOL | X-ray | 2.49 Å | A=24-290 |
| 5WHK | X-ray | 2.5 Å | A=1-297 |
| 3M17 | X-ray | 2.6 Å | A/C/E/G=24-290 |
| 9WYD | X-ray | 2.65 Å | A=24-297 |
| 1EXU | X-ray | 2.7 Å | A=24-290 |
| 6LA7 | EM | 2.82 Å | E=28-290 |
| 5BXF | X-ray | 2.85 Å | A/C=1-290 |
| 6FGB | X-ray | 2.9 Å | A=24-365 |
| 7B5F | EM | 2.9 Å | G=24-290 |
| 9OC6 | X-ray | 2.97 Å | C=24-297 |
Showing 20 of 30 experimental structures (best resolution first).
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