Crispr Associated Protein 9

An RNA-guided endodeoxyribonuclease that associates with CRISPR SEQUENCES in STREPTOCOCCUS PYOGENES and other bacteria where it participates in an adaptive immune function to cleave foreign DNA complimentary to small GUIDE RNA (sgRNAs). Structurally, Cas9 consists of an ALPHA-HELIX module and a nuclease module connected by a single helix. The nuclease module contains two enzymatic domains: RuvC, which cleaves non-target DNA strand, and an HNH nuclease domain, which cleaves the target strand. Specificity for the DNA target depends on the presence of a protospacer adjacent motif (PAM) sequence, a 2-6 nucleotide DNA sequence immediately following the sequence targeted by Cas9.