SNAP output for PDB entry 6vrc [SNAP web server]

PDB-id

6vrc; SNAP-derived features in text and JSON formats; DNAproDB

Class

immune system

Method

cryo-EM (3.2 Å)

Summary

cryo-EM structure of cas13(crrna)

Reference

Meeske AJ, Jia N, Cassel AK, Kozlova A, Liao J, Wiedmann M, Patel DJ, Marraffini LA (2020): "A phage-encoded anti-CRISPR enables complete evasion of type VI-A CRISPR-Cas immunity." Science, 369, 54-59. doi: 10.1126/science.abb6151.

Abstract

The CRISPR RNA (crRNA)-guided nuclease Cas13 recognizes complementary viral transcripts to trigger the degradation of both host and viral RNA during the type VI CRISPR-Cas antiviral response. However, how viruses can counteract this immunity is not known. We describe a listeriaphage (ϕLS46) encoding an anti-CRISPR protein (AcrVIA1) that inactivates the type VI-A CRISPR system of Listeria seeligeri Using genetics, biochemistry, and structural biology, we found that AcrVIA1 interacts with the guide-exposed face of Cas13a, preventing access to the target RNA and the conformational changes required for nuclease activation. Unlike inhibitors of DNA-cleaving Cas nucleases, which cause limited immunosuppression and require multiple infections to bypass CRISPR defenses, a single dose of AcrVIA1 delivered by an individual virion completely dismantles type VI-A CRISPR-mediated immunity.