Structure of the KsgA-RNA-SAH complex (Tu, Tropea, Austin, Court, Waugh and Ji. Structure 2009; 16:1417-1427. Abstract) superimposed with tetraloop RNA structures. KsgA is shown as a ribbon diagram in grey. SAH is shown as spheres (carbon in grey, nitrogen in blue, oxygen in red, and sulfur in yellow). RNAs are illustrated as tube-and-stick models with the positions of A1518 and A1519 indicated by spheres. RNA in the KsgA-RNA-SAH complex is shown in orange, the structure of product RNA with dimethylated A1518 and A1519 (PDB entry 2AW7) in cycan, and the model for substrate RNA with unmethylated adenosines (PDB entry 1AFX) in magenta.