Anti-CRISPR Protein AcrIIC5 Inhibits CRISPR-Cas9 by Occupying the Target DNA Binding Pocket
Bibliographic record
Abstract
Anti-CRISPR proteins inhibit CRISPR-Cas immune systems through diverse mechanisms. Previously, the anti-CRISPR protein AcrIIC5 Smu was shown to potently inhibit a type II-C Cas9 from Neisseria meningitidis (Nme1Cas9). In this work, we explore the mechanism of activity of the AcrIIC5 homologue from Neisseria chenwenguii (AcrIIC5 Nch ) and show that it prevents Cas9 binding to target DNA. We show that AcrIIC5 Nch targets the PAM-interacting domain (PID) of Nme1Cas9 for inhibition, agreeing with previous findings for AcrIIC5 Smu , and newly establish that strong binding of the anti-CRISPR requires guide RNA be pre-loaded on Cas9. We determined the crystal structure of AcrIIC5 Nch using X-ray crystallography and identified amino acid residues that are critical for its function. Using a protein docking algorithm we show that AcrIIC5 Nch likely occupies the Cas9 DNA binding pocket, thereby inhibiting target DNA binding through a mechanism similar to that previously described for AcrIIA2 and AcrIIA4.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".