CD81 antigen (CD81) is a 236-residue protein from Homo sapiens. This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: P60033.
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The mean pLDDT of this model is 87.4 (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 | 62% |
| 70 to 90 | Confident: backbone generally right | 28% |
| 50 to 70 | Low: treat with caution | 3% |
| Below 50 | Very low: often disordered regions | 6% |
What pLDDT means and how to read it
Structural component of specialized membrane microdomains known as tetraspanin-enriched microdomains (TERMs), which act as platforms for receptor clustering and signaling. Essential for trafficking and compartmentalization of CD19 receptor on the surface of activated B cells (PubMed:16449649, PubMed:20237408, PubMed:27881302). Upon initial encounter with microbial pathogens, enables the assembly of CD19-CR2/CD21 and B cell receptor (BCR) complexes at signaling TERMs, lowering the threshold dose of antigen required to trigger B cell clonal expansion and antibody production (PubMed:15161911, PubMed:20237408). In T cells, facilitates the localization of CD247/CD3 zeta at antigen-induced…
Homodimer (PubMed:20375010). Part of a complex composed of CD19, CR2/CD21, CD81 and IFITM1/CD225 in the membrane of mature B cells. Interacts (via the second extracellular domain) with CD19; this interaction is initiated early during biosynthesis in the ER and enables trafficking of only properly folded CD19 (PubMed:1383329, PubMed:16449649). Part of a complex that includes MHC class II/HLA-DR…
Cell membrane, Basolateral cell membrane
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 5M33 | X-ray | 1.28 Å | A/B=113-201 |
| 1G8Q | X-ray | 1.6 Å | A/B=113-202 |
| 3X0E | X-ray | 1.84 Å | A/B=113-202 |
| 5M2C | X-ray | 1.96 Å | A/B=112-201 |
| 5M3T | X-ray | 2.02 Å | A/B=112-201 |
| 6EJM | X-ray | 2.15 Å | A/B=112-202 |
| 5DFW | X-ray | 2.33 Å | A=112-201 |
| 5M3D | X-ray | 2.38 Å | A/B/C/D=112-201 |
| 6U9S | X-ray | 2.4 Å | C/F=112-200 |
| 1IV5 | X-ray | 2.6 Å | A/B=113-201 |
| 6EK2 | X-ray | 2.65 Å | A/B=112-201 |
| 5DFV | X-ray | 2.8 Å | A/B=112-202 |
| 6EJG | X-ray | 2.82 Å | A/B=112-202 |
| 5TCX | X-ray | 2.96 Å | A=2-236 |
| 5M4R | X-ray | 3.1 Å | A/B/C/D/E=112-201 |
| 7JIC | EM | 3.8 Å | B=2-236 |
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