Active site. MATα2 monomer with visible gating loop is coloured in slate whereas MATα2 monomer with disordered loops is coloured in red. Important hydrogen bonds are shown as dotted lines. (a) Stick representation of the bound product, SAMe, at the active site. (b) Crystal co-crystallized and soaked with only ATP shows adenosine molecule (ADO) and PO4 at the active site, as a result of the ATPases and tripolyphosphatase activity of MATα2. (c) Crystal co-crystallized and soaked with AMPPNP and methionine shows SAMe and PPNP. (d) Omit (Fo − Fc) electron-density map and stick representation of bound molecule, the map is contoured at the 2.5σ level around the SAMe molecule, (e) around the adenosine (ADO) molecule and (f) around SAMe and PPNP.