a–c Protein-cFA6 interactions. EiCsm6 is depicted in cartoon representation; cFA6 is shown as sticks. Hydrogen-bonding interactions are represented as black dotted lines. d Fluorogenic RNase activity assay of CARF domain mutants of EiCsm6 (0.5 nM) in the presence of 10 nM cyclic-hexa-AMP (cA6). AU, arbitrary units. e Growth curves (optical density at a wavelength of 600 nm) of Staphylococcus aureus strains harboring pTarget and pCRISPR plasmids. The pCRISPR plasmid expresses wild-type or CARF domain mutants of EiCsm6 and the Staphylococcus epidermidis Cas10–Csm effector complex containing an inactivating point mutation in the HD domain of Cas10. Data points in d, e represent the mean of three replicates; error bars represent the standard error of the mean (s.e.m.). Source data are provided as a Source Data file.