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). Optimal in vitro activity occurs in the presence of Mg(2+), but there is weak activity in its absence (PubMed:26593719). A more complete study shows a preference for Mn(2+), although activity is seen with Mg(2+) and Ca(2+) also (PubMed:27989439). Optimum temperature is 50 degrees Celsius cuts between 37 and 60 degrees Celsius. Monomer. Structures show 2 discontinuous REC (recognition, residues 15-386, 658-784) and NUC (nuclease, residues 1-14, 387-658 and 785-1129) lobes composed of several domains each; the boundaries given correspond to Lui et al., but Yang et al., differ only by a few residues in most cases (PubMed:27984729, PubMed:27989439). The crRNA (or single guide, sgRNA) binds in a central channel between the 2 lobes (PubMed:27984729, PubMed:27989439). PAM recognition is sequence specific and occurs mostly via interaction with the REC1 (helical-1) and WED-II (OBD-II) domains (PubMed:27984729). The sgRNA-target DNA heteroduplex binds primarily to the REC lobe in a sequence-independent manner (PubMed:27984729). The simplicity of the Cas12b-crRNA-tracrRNA endonuclease activity can be used in vitro to target and cleave a DNA sequence of interest, even in the presence of human cell lysate (PubMed:26593719). Fusion of the 5'-tracrRNA:crRNA-3' into a single-guide RNA (sgRNA) leads to a protein-sgRNA system that endonucleolytically cleaves target DNA in vitro (PubMed:26593719, PubMed:27984729, PubMed:27989439). Part of a type V-B CRISPR-Cas system.