CRISPR (clustered regularly interspaced short palindromic repeat), is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). Functions as a ssRNA-specific endoribonuclease. Involved in the integration of spacer DNA into the CRISPR cassette (By similarity). Homodimer, forms a heterotetramer with a Cas1 homodimer. Operon expression begins by 6 hours after starvation has initiated development and is under strong negative regulation by DevS. Part of an operon going from at least MXAN_7266 to MXAN_7259 that includes a CRISPR operon with transcription continuing into the pre-crRNA locus. Belongs to the CRISPR-associated endoribonuclease Cas2 protein family.