5′‐Deoxy‐5′‐methylthioadenosine phosphorylase (MTAP) catalyzes the phosphorolytic cleavage of 5′‐deoxy‐5′‐methylthioadenosine (MTA), a byproduct of polyamine biosynthesis. The Sulfolobus sulfataricus genome encodes
two MTAPs. SsMTAP I has broad substrate specifity, accepting guanosine, inosine, adenosine and MTA, while SsMTAP II is specific for MTA. SsMTAP I forms a donut‐shaped hexamer, while SsMTAP II is a hexamer formed from trimers packed face to face. The structure of SsMTAP II was originally
determined in space group P1 (PDB entry ) and showed R32 pseudosymmetry. Post‐analysis using phenix.xtriage showed that the correct space group is C2. Here, the structure refined in space group C2 is reported and the factors that initially led
to the incorrect space‐group assignment are discussed.