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). Processes pre-crRNA into individual crRNA units (By similarity). Complements a csy4 disruption in Pseudomonas aeruginosa PA14, restoring inhibition of biofilm formation and generation of crRNA. Belongs to the CRISPR-associated endoribonuclease Cas6 family. Cas6f/Csy4, subtype I-F/Ypest subfamily.