Complement C2 (C2) is a 752-residue protein from Homo sapiens. This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: P06681.
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The mean pLDDT of this model is 88.3 (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 | 66% |
| 70 to 90 | Confident: backbone generally right | 25% |
| 50 to 70 | Low: treat with caution | 4% |
| Below 50 | Very low: often disordered regions | 5% |
What pLDDT means and how to read it
Precursor of the catalytic component of the C3 and C5 convertase complexes, which are part of the complement pathway, a cascade of proteins that leads to phagocytosis and breakdown of pathogens and signaling that strengthens the adaptive immune system (PubMed:12878586, PubMed:17027507, PubMed:18204047, PubMed:39914456, PubMed:39814882). Component C2 is part of the classical, lectin and GZMK complement systems (PubMed:12878586, PubMed:17027507, PubMed:18204047, PubMed:22691502, PubMed:39914456)
Serine protease component of the C3 convertase, also named C4bC2b, composed of the serine protease complement C2b and complement C4b (PubMed:14561755, PubMed:27252379, PubMed:3874204, PubMed:6611150, PubMed:6906228). Serine protease component of the C5 convertase, also named C4bC2bC3b, composed of the serine protease complement C2b, complement C3b, as well as complement C4b (PubMed:12878586,…
Secreted, Cell surface
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 3ERB | X-ray | 1.8 Å | A=21-243 |
| 8ACF | X-ray | 1.8 Å | A=21-217 |
| 8ACI | X-ray | 1.85 Å | A=21-217 |
| 2ODP | X-ray | 1.9 Å | A=244-752 |
| 2I6Q | X-ray | 2.1 Å | A=242-752 |
| 2ODQ | X-ray | 2.3 Å | A=244-752 |
| 2I6S | X-ray | 2.7 Å | A=242-752 |
| 9U60 | EM | 2.9 Å | B=1-752 |
| 9U5Z | EM | 3.1 Å | B=1-752 |
| 9U61 | EM | 3.1 Å | B=244-752 |
| 9QJ5 | EM | 3.5 Å | D=1-752 |
| 9QK2 | EM | 3.5 Å | E=1-752 |
| 9QJ4 | EM | 3.9 Å | D=1-752 |
| 9QPY | EM | 4.3 Å | E=1-752 |
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