The Csc2 Crispr family of proteins forms a core RNA recognition motif-like domain, flanked by three peripheral insertion domains: a lid domain, a Zinc-binding domain and a helical domain [1]. The CRISPR-Cas system is possibly a mechanism of defence against invading pathogens and plasmids that functions analogously to the RNA interference (RNAi) systems in eukaryotes [2].

1: Structural analyses of the CRISPR protein Csc2 reveal the RNA-binding interface of the type I-D Cas7 family. Hrle A, Maier LK, Sharma K, Ebert J, Basquin C, Urlaub H, Marchfelder A, Conti E; RNA Biol. 2014;11:1072-1082. PMID:25483036

2: A putative RNA-interference-based immune system in prokaryotes: computational analysis of the predicted enzymatic machinery, functional analogies with eukaryotic RNAi, and hypothetical mechanisms of action. Makarova KS, Grishin NV, Shabalina SA, Wolf YI, Koonin EV; Biol Direct. 2006;1:7. PMID:16545108