CRISPR-associated endonuclease Cas9 (IPR028629)

Short name: Cas9

Overlapping homologous superfamilies


Family relationships



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 are transcribed and processed into CRISPR RNA (crRNA) to guide the silencing of invading nucleic acids. In type II CRISPR systems, correct processing of pre-crRNA requires a trans-encoded small RNA (tracrRNA), endogenous ribonuclease 3 (rnc) and this protein, Cas9 (Csn1) [PMID: 23563642]. The tracrRNA serves as a guide for ribonuclease 3-aided processing of pre-crRNA. Subsequently Cas9/crRNA/tracrRNA endonucleolytically cleaves linear or circular dsDNA target complementary to the spacer [PMID: 22745249]. Cas9 probably recognises a short motif in the CRISPR repeat sequences (the PAM or protospacer adjacent motif) to help distinguish self versus nonself.

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0004519 endonuclease activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.