EMD-4904

Single-particle
3.2 Å
EMD-4904 Deposition: 26/04/2019
Map released: 02/10/2019
Last modified: 22/05/2024
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links

EMD-4904

Cryo-EM structure of St1Cas9-sgRNA-AcrIIA6-tDNA59-ntPAM complex.

EMD-4904

Single-particle
3.2 Å
EMD-4904 Deposition: 26/04/2019
Map released: 02/10/2019
Last modified: 22/05/2024
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Sample Organism: Streptococcus virus 2972, Streptococcus phage D1811, Streptococcus thermophilus DGCC 7710, Streptococcus thermophilus
Sample: Cryo-EM structure of St1Cas9-sgRNA-AcrIIA6-tDNA59-ntPAM complex.
Fitted models: 6rjg (Avg. Q-score: 0.522)

Deposition Authors: Swuec P
Cas9 Allosteric Inhibition by the Anti-CRISPR Protein AcrIIA6.
PUBMED: 31604602
DOI: doi:10.1016/j.molcel.2019.09.012
ISSN: 1097-2765
ASTM: MOCEFL
Abstract:
In the arms race against bacteria, bacteriophages have evolved diverse anti-CRISPR proteins (Acrs) that block CRISPR-Cas immunity. Acrs play key roles in the molecular coevolution of bacteria with their predators, use a variety of mechanisms of action, and provide tools to regulate Cas-based genome manipulation. Here, we present structural and functional analyses of AcrIIA6, an Acr from virulent phages, exploring its unique anti-CRISPR action. Our cryo-EM structures and functional data of AcrIIA6 binding to Streptococcus thermophilus Cas9 (St1Cas9) show that AcrIIA6 acts as an allosteric inhibitor and induces St1Cas9 dimerization. AcrIIA6 reduces St1Cas9 binding affinity for DNA and prevents DNA binding within cells. The PAM and AcrIIA6 recognition sites are structurally close and allosterically linked. Mechanistically, AcrIIA6 affects the St1Cas9 conformational dynamics associated with PAM binding. Finally, we identify a natural St1Cas9 variant resistant to AcrIIA6 illustrating Acr-driven mutational escape and molecular diversification of Cas9 proteins.