Protein TonB (tonB) is a 239-residue protein from Escherichia coli (strain K12). This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: P02929.
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The mean pLDDT of this model is 74.8 (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 | 41% |
| 70 to 90 | Confident: backbone generally right | 8% |
| 50 to 70 | Low: treat with caution | 40% |
| Below 50 | Very low: often disordered regions | 10% |
What pLDDT means and how to read it
Interacts with outer membrane receptor proteins that carry out high-affinity binding and energy dependent uptake into the periplasmic space of specific substrates such as cobalamin, and various iron compounds (such as iron dicitrate, enterochelin, aerobactin, etc.). In the absence of TonB these receptors bind their substrates but do not carry out active transport. TonB also interacts with some colicins and is involved in the energy-dependent, irreversible steps of bacteriophages phi 80 and T1 infection. It could act to transduce energy from the cytoplasmic membrane to specific energy-requiring processes in the outer membrane, resulting in the release into the periplasm of ligands bound by…
Homodimer. Forms a complex with the accessory proteins ExbB and ExbD
Cell inner membrane
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 1U07 | X-ray | 1.13 Å | A/B=150-239 |
| 8VGC | X-ray | 1.42 Å | P=43-52 |
| 8VGD | X-ray | 1.42 Å | P=43-51 |
| 8P9R | X-ray | 1.52 Å | C=40-62 |
| 1IHR | X-ray | 1.55 Å | A/B=164-239 |
| 2GSK | X-ray | 2.1 Å | B=153-233 |
| 1QXX | X-ray | 2.7 Å | A=164-239 |
| 9DDO | EM | 2.8 Å | F=1-239 |
| 9DDP | EM | 3.16 Å | F=1-239 |
| 9DDQ | EM | 3.19 Å | F=1-239 |
| 2GRX | X-ray | 3.3 Å | C/D=29-239 |
| 1XX3 | NMR | A=103-239 |
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