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Table 1 Key differences between the Cas9 and Cas12a CRISPR proteins

From: CRISPR–Cas ribonucleoprotein mediated homology-directed repair for efficient targeted genome editing in microalgae Nannochloropsis oceanica IMET1

Feature Cas9 Cas12a (Cpf1)
CRISPR enzyme Class 2, Type II-B
Molecular weight: ~ 164 kDa
Endonuclease domains: RuvC and HNH
Class 2, Type V-A
Molecular weight: ~ 158 kDa
Endonuclease domains: RuvC only
guideRNA ~ 120 nt, two RNA sequences crRNA and tracrRNA are synthetically fused to form the single guide RNA (sgRNA) ~ 43 nt, only crRNA is required
crRNA maturation RNase III dependent RNase III independent, autonomous processing
DSB cleavage site 3 bases upstream of the protospacer sequence
PAM site often destroyed during genome editing
18–23 bases downstream of the PAM
PAM site may be preserved after genome editing
DSB cleavage mechanism Blunt end cuts 5-nt staggered end cut distal to the PAM