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). A component of Cascade, which participates in CRISPR interference, the third stage of CRISPR immunity. Cascade binds both crRNA and in a sequence-specific manner negatively supercoiled dsDNA target. This leads to the formation of an R-loop in which the crRNA binds the target DNA, displacing the noncomplementary strand. Cas3 is recruited to Cascade, nicks target DNA and then unwinds and cleaves the target, leading to DNA degradation and invader neutralization. CasCDE alone is also able to form R-loops. Part of the Cascade ribonucleoprotein complex, with stoichiometry CasA(1),CasB(2),CasC(6),CasD(1),CasE(1)-crRNA(1). Interacts directly with CasA and CasC. Stable subcomplexes of CasBCDE-crRNA and CasCDE-crRNA also form, both of which are able to bind target dsDNA, and at least CasCDE is able to form R-loops. CasCDE and CasCE complexes have endonuclease activity. Binding of target ssRNA or dsDNA causes a conformational change in the Cascade complex. Repressed by H-NS, activated by LeuO. Activated by the BaeSR two-component regulatory system, possibly due to envelope stress. Part of the casABCDE-ygbT-ygbF operon. Loss of resistance to bacteriophage lambda infection, loss of plasmid silencing. Decreased levels of crRNA. Belongs to the CRISPR-associated protein Cas5 family. Subtype I-E/Ecoli subfamily. Extended N-terminus.