CRISPR-associated endonuclease Cas12b

UniProtKB accession:  T0D7A2

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UniProtKB description:  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). In type II CRISPR systems correct processing of pre-crRNA requires a trans-encoded small RNA (tracrRNA), endogenous ribonuclease 3 (rnc) and this protein (By similarity). The tracrRNA serves as a guide for ribonuclease 3-aided processing of pre-crRNA (By similarity). Protein-crRNA-tracrRNA endonucleolytically cleave dsDNA target complementary to the spacer; protein is inactive in the absence of crRNA homologous to the target and tracrRNA (PubMed:26593719). Recognizes a short motif in the CRISPR repeat sequences (the 5' PAM or protospacer adjacent motif, TTN in this organism) to help distinguish self versus nonself, as targets within the bacterial CRISPR locus do not have PAMs (PubMed:26593719). PAM recognition is also required for catalytic activity. Cleavage results in staggered 6-8 base 5'-overhangs 14-17 and 23-24 bases downstream of the PAM (protospacer adjacent motif) on the non-target and target strands respectively (PubMed:27984729, PubMed:27989439). Both target and non-target strand DNA are probably independently cleaved in the same active site (PubMed:27984729).