Complement component C9 (C9) is a 559-residue protein from Homo sapiens. This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: P02748.
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The mean pLDDT of this model is 78.8 (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 | 39% |
| 70 to 90 | Confident: backbone generally right | 39% |
| 50 to 70 | Low: treat with caution | 7% |
| Below 50 | Very low: often disordered regions | 16% |
What pLDDT means and how to read it
Pore-forming component of the membrane attack complex (MAC), a multiprotein complex activated by the complement cascade, which inserts into a target cell membrane and forms a pore, leading to target cell membrane rupture and cell lysis (PubMed:22832194, PubMed:26841837, PubMed:26841934, PubMed:27052168, PubMed:30552328, PubMed:6177822, PubMed:9212048, PubMed:9634479). The MAC is initiated by proteolytic cleavage of C5 into complement C5b in response to the classical, alternative, lectin and GZMK complement pathways (PubMed:39914456, PubMed:39814882, PubMed:9212048, PubMed:9634479). The complement pathways consist in a cascade of proteins that leads to phagocytosis and breakdown of…
Homooligomer; about 20 C9 chains oligomerize to give rise to a huge beta-barrel that forms a 100 Angstrom diameter pore in target membranes (PubMed:26841934, PubMed:30111885, PubMed:34752492). Component of the membrane attack complex (MAC), composed of complement C5b, C6, C7, C8A, C8B, C8G and multiple copies of the pore-forming subunit C9 (PubMed:22832194, PubMed:26841837, PubMed:26841934,…
Secreted, Target cell membrane
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 8DE6 | EM | 3.2 Å | A/C/G=21-559 |
| 7NYD | EM | 3.3 Å | G/H=22-559 |
| 8B0G | EM | 3.3 Å | H/I/J=1-559 |
| 8B0H | EM | 3.3 Å | H/I=1-559 |
| 7NYC | EM | 3.5 Å | G/H/I=22-559 |
| 6DLW | EM | 3.9 Å | A/B/C/D/E/F/G/H/I/J/K/L/M/N/O/P/Q/R/S/T/U/V=22-559 |
| 6H03 | EM | 5.6 Å | G/H/I/J/K/L/M/N/O/P/Q/R/S/T/U/V/W/X=22-559 |
| 6H04 | EM | 5.6 Å | G/H/I/J/K/L/M/N/O/P/Q/R/S/T/U/V/W/X=22-559 |
| 5FMW | EM | 6.7 Å | A/B/C/D/E/F/G/H/I/J/K/L/M/N/O/P/Q/R/S/T/U/V=39-544 |
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