Fig. (5) (Left) X-ray crystal structure of JMJD2A (blue) in complex with NOG (2-OG cofactor isostere) and a histone H3KMe3 peptide (red). (Right) Close-up view of active site: the Fe(II)-is complexed by a facial triad of a single glutamate or aspartate and two histidine residues, and the methylated lysine side-chain inserts into a relatively large cavity bounded by several aromatic residues, with the methylamino group positioned close to the Fe(II) for hydroxylation.