CRISPR system Cascade subunit CasA (casA) is a 502-residue protein from Escherichia coli (strain K12). This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: Q46901.
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The mean pLDDT of this model is 93.0 (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 | 85% |
| 70 to 90 | Confident: backbone generally right | 12% |
| 50 to 70 | Low: treat with caution | 2% |
| Below 50 | Very low: often disordered regions | 1% |
What pLDDT means and how to read it
CRISPR (clustered regularly interspaced short palindromic repeat), is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA)
Part of the Cascade ribonucleoprotein complex, with stoichiometry CasA(1),CasB(2),CasC(6),CasD(1),CasE(1)-crRNA(1). Interacts directly with the 5' end of crRNA, CasB, CasD and CasE. Binding of target ssRNA or dsDNA causes a conformational change in the Cascade complex; CasA is required for high affinity target DNA binding. Interacts with Cas3 once Cascade has recognized target DNA
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 5H9F | X-ray | 2.45 Å | A=1-502 |
| 4U7U | X-ray | 3.0 Å | A/M=1-502 |
| 4QYZ | X-ray | 3.03 Å | A=1-502 |
| 5CD4 | X-ray | 3.2 Å | I/U=1-502 |
| 5H9E | X-ray | 3.21 Å | A=1-502 |
| 4TVX | X-ray | 3.24 Å | I/U=1-502 |
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