Structural aspects of nucleotide ligand binding by a bacterial 2H phosphoesterase

Myllykoski, Matti; Kursula, Petri

The LigT structure presents a typical 2H phosphoesterase fold, in which the catalytic residues reside at the beginning of strands β2 and β6 ( Fig 1A) . As in other 2H family members, the active site has 2-fold symmetry; this symmetry also includes the 4 water molecules at the bottom of the active site, connecting the active-site β strands through water-mediated hydrogen bonds ( Fig 1B) . These water molecules coordinate the substrate/product throughout the reaction in CNPase [17, 18] , and they are likely to play a similar role in LigT and other 2H phosphoesterases. The strict conservation of the active-site water structure between 2H enzymes is remarkable, taking into account the amino acid sequence identity of slightly above 10% between CNPase and LigT.