Cholera enterotoxin subunit A (ctxA) is a 258-residue protein from Vibrio cholerae serotype O1 (strain ATCC 39315 / El Tor Inaba N16961). This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: P01555.
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The mean pLDDT of this model is 89.0 (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 | 76% |
| 70 to 90 | Confident: backbone generally right | 12% |
| 50 to 70 | Low: treat with caution | 8% |
| Below 50 | Very low: often disordered regions | 4% |
What pLDDT means and how to read it
The A1 chain catalyzes the ADP-ribosylation of Gs alpha, a GTP-binding regulatory protein, to activate the adenylate cyclase. This leads to an overproduction of cAMP and eventually to a hypersecretion of chloride and bicarbonate followed by water, resulting in the characteristic cholera stool. The A2 chain tethers A1 to the pentameric ring
The holotoxin (choleragen) consists of a pentameric ring of B subunits whose central pore is occupied by the A subunit. The A subunit contains two chains, A1 and A2, linked by a disulfide bridge. Interaction with the host protein ARF6 causes a conformation change so that the enterotoxin subunit A1 can bind NAD and catalyze the ADP-ribosylation of the host Gs alpha
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 8OXS | X-ray | 1.6 Å | A/B=19-258 |
| 8Q6I | X-ray | 1.6 Å | A=19-258 |
| 1S5D | X-ray | 1.75 Å | A=19-258 |
| 2A5D | X-ray | 1.8 Å | B=19-210 |
| 1S5E | X-ray | 1.9 Å | A/B=19-258 |
| 2A5F | X-ray | 2.02 Å | B=19-210 |
| 1S5B | X-ray | 2.13 Å | A=19-258 |
| 8QRE | X-ray | 2.3 Å | A/B=19-258 |
| 1XTC | X-ray | 2.4 Å | A=19-212, C=213-258 |
| 1S5C | X-ray | 2.5 Å | A=19-258 |
| 1S5F | X-ray | 2.6 Å | A=19-258 |
| 2A5G | X-ray | 2.66 Å | B=19-210 |
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