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Publication Abstract from PubMed

Bacteria use adaptive CRISPR-Cas immune mechanisms to protect from invasion by bacteriophages and other mobile genetic elements. In response, bacteriophages and mobile genetic elements have co-evolved anti-CRISPR proteins to inhibit the bacterial defense. We and others have previously shown that anti-CRISPR associated (Aca) proteins can regulate this anti-CRISPR counter-attack. Here, we report the first structure of an Aca protein, the Aca2 DNA-binding transcriptional autorepressor from Pectobacterium carotovorum bacteriophage ZF40, determined to 1.34 A. Aca2 presents a conserved N-terminal helix-turn-helix DNA-binding domain and a previously uncharacterized C-terminal dimerization domain. Dimerization positions the Aca2 recognition helices for insertion into the major grooves of target DNA, supporting its role in regulating anti-CRISPRs. Furthermore, database comparisons identified uncharacterized Aca2 structural homologs in pathogenic bacteria, suggesting that Aca2 represents the first characterized member of a more widespread family of transcriptional regulators.

Crystal structure of the anti-CRISPR repressor Aca2.,Usher B, Birkholz N, Beck IN, Fagerlund RD, Jackson SA, Fineran PC, Blower TR J Struct Biol. 2021 Jun 8;213(3):107752. doi: 10.1016/j.jsb.2021.107752. PMID:34116143^[1]

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