Table 1.
Details on classification of CRISPR/Cas systems. The details such as class, type, protein name, target molecule, mechanism of spacer acquisition, processing of Pre-CRISPR, self vs non-self-discrimination, and host organism are included with their references
| Class | Type | Protein | Target | Spacer acquisition of CRISPR system | Interference of CRISPR system | Pre-CRISPR processing | Self vs non-self discrimination |
Host organism | References |
|---|---|---|---|---|---|---|---|---|---|
| Class 1 | I | Cas3 | ssDNA | Cas1/Cas2/ Cas4 | Cas7, Cas5, Cas8, and Cas3 | Cas6 | PAM | E. coli | [45] |
| III | Cas10 | ssDNA | Cas1/Cas2 | Cas7, Cas5, and Cas1 | Cas6 | CRISPR Repeat | S. epidermics | [43] | |
| IV | Csf1 | - | NA | Cas7, Cas5, and Csf1 | - | - | - | [34] | |
| Class 2 | II | Cas9 | dsDNA | Cas1/Cas2/ Cas4 | Cas9 | RNase III, and tracrRNA |
PAM |
S. thermophilus and S. pyogenes |
[15,44] |
| V | Cpf1 | ssDNA and dsDNA | Cas1/Cas2/ Cas4 | Cas12 | Cpf1 | PAM | F. novicida | [50] | |
| VI | C2c2 | ssRNA | Cas1/Cas2 | Cas13 | - | - | - | [57] |
PAM, protospacer adjacent motif; Cpf1, CRISPR-associated endonuclease in Prevotella and Francisella 1; tracrRNA, trans-activating CRISPR RNA, E. coli, Escherichia coli; S. epidermics, streptococcus epidermics; F. novicida, Francisella novicida