Table 1.

Current characterization of Type II, V and VI effectors

Effectora	Cas9	Cas12a	Cas13a	Cas13b	Cas13d
Subtype	II-A	V-A	VI-A	VI-B	VI-D
Target	dsDNA	dsDNA	ssRNA	ssRNA	ssRNA
Nuclease domainb	RuvC-NTS, HNH-TS	RuvC-NTS, TS Nuc	2 HEPN	2 HEPN	2 HEPN
Pre-crRNA processing	RNase III	WED III	Helical 1 or HEPN2	?	?
tracrRNA	Yes	No	No	No	No
Cut nature	Staggered, 5′ 1- or 3-nt overhangs	Staggered, 5 nt overhangs collateral activity-ssDNA	Collateral activity-ssRNA	Collateral activity-ssRNA	Collateral activity-ssRNA
PAM/PFSc	3′G-rich PAM	5′T-rich PAM	3′ PFS: H	5′PFS: D;3′ PFS:NAN or NNA	No?
Median size	1228 aa	1268 aa	1228 aa	1128 aa	928 aa

^a Characterized and validated types are included

^b TS and NTS indicate domain that cleaves target strand (TS) or non-target strand (NTS)

^c D: A, G, or U; H: A, C, or U; N: A, C, G, or T (or U)