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Publication Abstract from PubMed

Prokaryotes evolved clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) proteins as a kind of adaptive immune defense against mobile genetic elements including harmful phages. To counteract this defense, many mobile genetic elements in turn encode anti-CRISPR proteins (Acrs) to inactivate the CRISPR-Cas system. While multiple mechanisms of Acrs have been uncovered, it remains unknown whether other mechanisms are utilized by uncharacterized Acrs. Here, we report a novel mechanism adopted by recently identified AcrIF23. We show that AcrIF23 interacts with the Cas2/3 helicase-nuclease in the type I-F CRISPR-Cas system, similar to AcrIF3. The structure of AcrIF23 demonstrated a novel fold and structure-based mutagenesis identified a surface region of AcrIF23 involved in both Cas2/3-binding and its inhibition capacity. Unlike AcrIF3, however, we found AcrIF23 only potently inhibits the DNA cleavage activity of Cas2/3 but does not hinder the recruitment of Cas2/3 to the CRISPR RNA-guided surveillance complex (the Csy complex). Also, in contrast to AcrIF3 which hinders substrate DNA recognition by Cas2/3, we show AcrIF23 promotes DNA binding to Cas2/3. Taken together, our study identifies a novel anti-CRISPR mechanism used by AcrIF23 and highlights the diverse mechanisms adopted by Acrs.

Structural and mechanistic insights into the inhibition of type I-F CRISPR-Cas system by anti-CRISPR protein AcrIF23.,Ren J, Wang H, Yang L, Li F, Wu Y, Luo Z, Chen Z, Zhang Y, Feng Y J Biol Chem. 2022 Jul;298(7):102124. doi: 10.1016/j.jbc.2022.102124. Epub 2022, Jun 10. PMID:35697070^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.