 Furthermore, AcrIIC3 prevents DNA binding by promoting dimerization of Cas9  and AcrIIA2 mimics DNA, thereby blocking the PAM recognition residues and consequently preventing dsDNA "(double-stranded DNA)" recognition and binding.AcrE1, AcrIF3 and AcrIIC1 can prevent target DNA cleavage.Using X-ray crystallography, AcrE1 was discovered to bind to the CRISPR associated Cas3.