Photosystem I iron-sulfur center (psaC) is a 81-residue protein from Thermosynechococcus vestitus (strain NIES-2133 / IAM M-273 / BP-1). This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: P0A415.
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The mean pLDDT of this model is 90.3 (very high 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 | 69% |
| 70 to 90 | Confident: backbone generally right | 30% |
| 50 to 70 | Low: treat with caution | 1% |
| Below 50 | Very low: often disordered regions | 0% |
What pLDDT means and how to read it
Apoprotein for the two 4Fe-4S centers FA and FB of photosystem I (PSI); essential for photochemical activity. FB is the terminal electron acceptor of PSI, donating electrons to ferredoxin. The C-terminus interacts with PsaA/B/D and helps assemble the protein into the PSI complex. Required for binding of PsaD and PsaE to PSI. PSI is a plastocyanin/cytochrome c6-ferredoxin oxidoreductase, converting photonic excitation into a charge separation, which transfers an electron from the donor P700 chlorophyll pair to the spectroscopically characterized acceptors A0, A1, FX, FA and FB in turn
The cyanobacterial PSI reaction center is composed of one copy each of PsaA,B,C,D,E,F,I,J,K,L,M and X, and forms trimeric complexes
Cellular thylakoid membrane
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 7FIX | EM | 1.97 Å | C1/C2/C3=1-81 |
| 1JB0 | X-ray | 2.5 Å | C=2-81 |
| 7M75 | X-ray | 2.75 Å | C=2-81 |
| 6TRA | EM | 2.85 Å | C=1-81 |
| 6PFY | X-ray | 2.9 Å | C/N/a=1-81 |
| 6PGK | X-ray | 2.9 Å | C/N/a=1-81 |
| 6TRC | EM | 2.98 Å | 3/C/c=1-81 |
| 7M76 | X-ray | 3.0 Å | C=2-81 |
| 7M78 | X-ray | 3.0 Å | C=2-81 |
| 6TRD | EM | 3.16 Å | 3/C/c=1-81 |
| 6LU1 | EM | 3.2 Å | C=1-81 |
| 9LZJ | EM | 3.4 Å | aC/bC/cC=1-81 |
| 9LZK | EM | 3.5 Å | C=1-81 |
| 1C51 | X-ray | 4.0 Å | - |
| 2PPS | X-ray | 4.0 Å | - |
| 5ZF0 | X-ray | 4.2 Å | C1/C2/C3/C4/C5/C6=2-81 |
| 4FE1 | X-ray | 4.92 Å | C=2-81 |
| 7BW2 | X-ray | 6.5 Å | C=1-81 |
| 3PCQ | X-ray | 8.98 Å | C=2-81 |
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