7tax
From Proteopedia
Cryo-EM structure of the Csy-AcrIF24-promoter DNA complex
Structural highlights
FunctionCSY1_PSEAB 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. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). Cas3 and Cascade participate in CRISPR interference, the third stage of CRISPR immunity (Potential). Involved in crRNA production or stability. The Csy ribonucleoprotein complex binds target ssDNA with high affinity but target dsDNA with much lower affinity.[1] [2] Publication Abstract from PubMedAnti-CRISPR (Acr) proteins are encoded by phages to inactivate CRISPR-Cas systems of bacteria and archaea and are used to enhance the CRISPR toolbox for genome editing. Here we report the structure and mechanism of AcrIF24, an Acr protein that inhibits the type I-F CRISPR-Cas system from Pseudomonas aeruginosa. AcrIF24 is a homodimer that associates with two copies of the surveillance complex (Csy) and prevents the hybridization between CRISPR RNA and target DNA. Furthermore, AcrIF24 functions as an anti-CRISPR-associated (Aca) protein to repress the transcription of the acrIF23-acrIF24 operon. Alone or in complex with Csy, AcrIF24 is capable of binding to the acrIF23-acrIF24 promoter DNA with nanomolar affinity. The structure of a Csy-AcrIF24-promoter DNA complex at 2.7 A reveals the mechanism for transcriptional suppression. Our results reveal that AcrIF24 functions as an Acr-Aca fusion protein, and they extend understanding of the diverse mechanisms used by Acr proteins. Structural basis of AcrIF24 as an anti-CRISPR protein and transcriptional suppressor.,Mukherjee IA, Gabel C, Noinaj N, Bondy-Denomy J, Chang L Nat Chem Biol. 2022 Dec;18(12):1417-1424. doi: 10.1038/s41589-022-01137-w. Epub , 2022 Sep 26. PMID:36163386[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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