Table 2.

Summary of known Anti-CRISPR mechanisms

Regulator	Acr type	Key Mechanism
AcrF120	Competitive	- Blocks dsDNA binding by interacting with Cas7f
AcrF220		- Blocks dsDNA binding by wedging between Cas8f and Cas7.6f
AcrF322		- Interacts with Cas3 and blocks its interaction with Csy complex
AcrF10100		- Blocks dsDNA binding by making contacts with Cas5f, 7f and 8f.
AcrIIA225	Competitive	- Blocks dsDNA by interacting with PAM interaction sites on Cas9
AcrIIA426		- Blocks dsDNA by interacting with PAM interaction sites on Cas9
AcrIIC123		- Inhibits catalytic activity of Cas9 by interacting with the HNH domain
AcrIIC224		- Interacts with the bridge-helix region of Cas9 and blocks guide RNA binding
AcrVIA127,72	Competitive	- Blocks target RNA binding by interacting with the crRNA, Helical-1, NTD, HEPN-1, and Linker domains of Cas13a-crRNA complex
AcrIIA628	Allosteric	- Interacts as a dimer with the Cas9-sgRNA complex formed by WED and PAM-interacting domain reducing target DNA binding.
AcrIIC323		- Interacts as a dimer with non-catalytic sites of HNH and dimerizes Cas9 to prevent dsDNA binding
AcrVA429	Allosteric	- Interacts as a dimer with Cas12a at the WED and bridge-helix to prevent stable dsDNA interaction.
AcrIII133	Enzymatic	- Degrades cOAs through its ring nuclease activity
AcrVA131	Enzymatic	- Occupies PAM binding groove on Cas12a-crRNA complex and endoribonucleolytically cleaves crRNA
AcrVA532		- Acetylates Lys635 on Cas12a and prevents dsDNA binding