Immunoglobulin G-binding protein A (spa) is a 516-residue protein from Staphylococcus aureus (strain NCTC 8325 / PS 47). This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: P02976.
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The mean pLDDT of this model is 68.3 (low 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 | 32% |
| 70 to 90 | Confident: backbone generally right | 27% |
| 50 to 70 | Low: treat with caution | 5% |
| Below 50 | Very low: often disordered regions | 36% |
What pLDDT means and how to read it
Plays a role in the inhibition of the host innate and adaptive immune responses. Possesses five immunoglobulin-binding domains that capture both the fragment crystallizable region (Fc region) and the Fab region (part of Ig that identifies antigen) of immunoglobulins (PubMed:10805799, PubMed:2938951, PubMed:4163007). In turn, Staphylococcus aureus is protected from phagocytic killing via inhibition of Ig Fc region. In addition, the host elicited B-cell response is prevented due to a decrease of antibody-secreting cell proliferation that enter the bone marrow, thereby decreasing long-term antibody production. Inhibits osteogenesis by preventing osteoblast proliferation and expression of…
Interacts with host TNFRSF1A; this interaction leads to the stimulation of both surface expression and shedding of TNFRSF1A. Interacts (via B domain) with IgG1, IgG2 and IgG4; spa interferes with IgG oligomerization and IgG:C1 complement complex formation, preventing complement activation and ultimately protecting bacteria from phagocytic killing
Secreted, cell wall, Secreted
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 8DA5 | X-ray | 1.0 Å | A/C=212-269 |
| 8DA7 | X-ray | 1.02 Å | A=213-269 |
| 8DA3 | X-ray | 1.06 Å | A=213-269 |
| 8DAB | X-ray | 1.13 Å | A=213-269 |
| 8DAC | X-ray | 1.19 Å | A=213-269 |
| 8DA8 | X-ray | 1.29 Å | A=213-269 |
| 8DA9 | X-ray | 1.35 Å | A/C=213-269 |
| 9M6O | X-ray | 1.49 Å | A/H=93-153 |
| 8DA6 | X-ray | 1.5 Å | A/C=213-269 |
| 6K65 | X-ray | 1.65 Å | A=218-266 |
| 5U6A | X-ray | 1.74 Å | C=101-151 |
| 8DAA | X-ray | 1.75 Å | A/C=213-269 |
| 5U3D | X-ray | 1.77 Å | C=101-151 |
| 6K3M | X-ray | 1.8 Å | H=100-150 |
| 5U5F | X-ray | 1.81 Å | C=101-151 |
| 6B9Z | X-ray | 1.82 Å | C=101-151 |
| 5U5M | X-ray | 1.88 Å | C=101-151 |
| 6BAH | X-ray | 1.9 Å | C=101-151 |
| 8DA4 | X-ray | 1.92 Å | A/C/E=213-269 |
| 6K64 | X-ray | 1.93 Å | C/H=100-151 |
Showing 20 of 38 experimental structures (best resolution first).
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