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. 2022 Sep 27;65(3):311–325. doi: 10.1007/s12033-022-00567-0

Table 1.

Classification of CRISPR/Cas system with their protein, target molecule, mechanism of spacer acquisition, processing of Pre-CRISPR, self-vs non-self-discrimination and their effectors with the name of isolated organism with references

Class Type Protein Target Spacer acquisition strategy Name of CRISPR/Cas system Pre-CRISPR processing Self vs nonself-discrimination Effectors of CRISPR system Host organism References
Class1 I Cas3 ssDNA Cas1/Cas2/ Cas4 Cas7, Cas5, Cas8, and Cas3 Cas6 PAM Cas3, Cascade, and crRNA E. coli [23]
III Cas10 ssDNA Cas1/Cas2 Cas7, Cas5, and Cas1 Cas6 CRISPR repeat Cmr/Csm, crRNA, and Cas10 S. epidermics [24]
IV Csf1 NA Cas7, Cas5, and Csf1 [21]
Class2 II Cas9 dsDNA Cas1/Cas2/ Cas4 Cas9 RNase III, and tracrRNA PAM Cas9, tracrRNA, and crRNA S. thermophilus and S. pyogenes [8]
V Cpf1 ssDNA and dsDNA Cas1/Cas2/ Cas4 Cas12 Cpf1 PAM Cpf1, crRNA and tracrRNA F. novicida [25]
VI C2c2 ssRNA Cas1/Cas2 Cas13 C2c1, and crRNA [26]