A new use for a familiar fold: the X-ray crystal structure of GTP-bound GTP cyclohydrolase III from Methanocaldococcus jannaschii reveals a two metal ion catalytic mechanism

The X-ray crystal structure of GTP cyclohydrolase (GCH) III from Methanocaldococcus jannaschii (MJ0145) bound to its substrate GTP is determined. The arrangement of metal ions in the active site has suggested that GCH III has used two metal ion catalysis and the structure of GCH III has extended the repertoire of the reactions with a palm fold to include cyclohydrolase chemistry.