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Table 1 Differences between type I, II, III, and V CRISPR/Cas systems

From: Application of different types of CRISPR/Cas-based systems in bacteria

Classification Type I Type II Type III Type V
Signature protein Cas3 (or Cas3′) Cas9 (1368 amino acids) Csm (III-A) or
Cmr (III-B)
Cas12a
(1200–1300 amino acids)
Effector Cascade crRNA and tracrRNA (sgRNA) Cascade crRNA
PAM sequence 3-nt G-rich sequence, 5′-NGG-3′ Without PAM 5′-YTN-3′(FnCas12a), 5′-TTTN-3′(AsCas12a, LbCas12a)
Cleavage product SSBs DSB (flat end) SSBs at every 6-nt DSB (Sticky end with 5 nucleotides protruding)