The putative catalytic center of KsgA as observed in the KsgA-RNA-SAH complex (in green, Tu, Tropea, Austin, Court, Waugh and Ji. Structure 2009; 16:1417-1427. Abstract) superimposed with the catalytic assembly of M-TaqI as observed in the M-TaqI-DNA-NEA structure (in gellow, PDB entry 1G38). The alignment was based on the cofactor SAH (stick model with carbon in green, nitrogen in blue, oxygen in red and sulfur in yellow) and the cofactor analog NEA (stick model with carbon in yellow). The target adenine dA606 for M-TaqI is shown as a stick model in magenta, whereas the A1518 and A1519 for KsgA are shown as stick models in red. The contact between atom N6 of dA606 in the M-TaqI complex and atom S of SAH in teh KsgA complex is indicated with a dashed line in black.