Structural basis for inhibition of an archaeal CRISPR–Cas type I-D large subunit by an anti-CRISPR protein

In type I-D CRISPR–Cas systems, the nuclease and helicase activities are carried out by separate subunits. The crystal structure of Sulfolobus islandicus type I-D large subunit Cas10d, containing a nuclease domain, reveals unusual architecture. The structure of Cas10d in complex with anti-CRISPR protein AcrID1 suggests that the latter sequesters Cas10d in a nonfunctional state.