6vrc | pdb_00006vrc
Cryo-EM structure of Cas13(crRNA)
Structural highlights
Function[CS13A_LISSS] 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. Unlike many single-component effectors, this CRISPR-Cas system targets RNA (By similarity). CRISPR clusters are transcribed from pre-CRISPR RNA (crRNA) and processed into crRNA by this protein (PubMed:27669025).[UniProtKB:P0DOC6][1] Publication Abstract from PubMedThe 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. How viruses can counteract this immunity is not known. We describe a listeriophage (varphiLS46) encoding an anti-CRISPR protein (AcrVIA1) that inactivated the type VI-A CRISPR system of Listeria seeligeri Using genetics, biochemistry and structural biology we found that AcrVIA1 interacted 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 could completely dismantle type VI-A CRISPR-mediated immunity. A phage-encoded anti-CRISPR enables complete evasion of type VI-A CRISPR-Cas immunity.,Meeske AJ, Jia N, Cassel AK, Kozlova A, Liao J, Wiedmann M, Patel DJ, Marraffini LA Science. 2020 May 28. pii: science.abb6151. doi: 10.1126/science.abb6151. PMID:32467331[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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