Fig. 4: Detailed interactions between AcrIF24 and the Csy complex, which is essential to the inhibition capacity.

a Overall structure of the Csy-AcrIF24 complex with one AcrIF24 bound to one Csy complex. The Csy complex is shown in the surface model with each subunit colored as in Fig. 3d. AcrIF24 is shown in cartoon model colored in yellow, hot pink, and cyan for its NTD, MD, and CTD, respectively. b–e Close-up view of the interfaces between AcrIF24 and the Csy complex. The interfaces of AcrIF24^NTD-Cas7.6f (b), AcrIF24^NTD-Cas7.5f (c), AcrIF24^MD-Cas7.4f (d), and AcrIF24^MD-Cas7.2f (e) are shown. AcrIF24 is colored as in a, and interacting residues are shown as sticks with cryo-EM density map shown in mesh. f Native gel was used to test the binding between the Csy complex and AcrIF24 or its mutants. Reactions were performed with 0.32 μM Csy complex and AcrIF24 concentrations of 0.16, 0.32, and 0.64 μM following the order indicated by the black triangle. DDRF/AAAA represents the D104A/D105A/R106A/F107A mutant. The gel was stained with Coomassie blue staining. g Mutations of the interface residues of AcrIF24 decreased its inhibition capacity of the in vitro cleavage activity of the type I-F CRISPR system. Reactions are performed as in Fig. 1a. DDRF/AAAA represents the D104A/D105A/R106A/F107A mutant.