CRISPR-associated endoribonuclease Cas13a (cas13a) is a 1159-residue protein from Leptotrichia buccalis (strain ATCC 14201 / DSM 1135 / JCM 12969 / NCTC 10249 / C-1013-b). This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: C7NBY4.
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The mean pLDDT of this model is 88.0 (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 | 56% |
| 70 to 90 | Confident: backbone generally right | 38% |
| 50 to 70 | Low: treat with caution | 5% |
| 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 (spacer sequences) and target invading nucleic acids. Unlike many single-component effectors, this CRISPR-Cas system targets RNA (PubMed:27669025). CRISPR clusters are transcribed from pre-CRISPR RNA (crRNA) and processed into crRNA by this protein (PubMed:27669025, PubMed:28475872, PubMed:28757251). pre-crRNA processing yields a 5'-OH and probably a 2',3'-cyclic phosphate (PubMed:27669025). Also cleaves…
Crystals show the 3'-end of target RNA interacting with an adjacent protein molecule, and mutagenesis of those amino acid residues decreases target RNA cleavage, but it is not clear if this is physiological (PubMed:28757251)
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 5XWP | X-ray | 3.08 Å | A/B=1-1159 |
| 5XWY | EM | 3.2 Å | A=1-1159 |
| 9MVS | EM | 3.43 Å | A=1-1159 |
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