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

Myllykoski, Matti; Kursula, Petri

In a recent study, E. coli LigT was crystallized, and its structure was refined in complex with the in vitro reaction product 2 0 -AMP [22] . We extend the previous study here, providing highresolution crystallographic data and different active-site ligand complexes. Comparisons to the apo form of the enzyme determined in the current work allow the highlighting of conformational changes and binding determinants of the reactive species. Based on further comparisons to mouse CNPase, we also modelled the substrate complex of LigT and discuss unique features of each protein. An extended binding surface for RNA substrates is also identified, which possibly involves flexible loops of the 2H family. All in all, we provide novel data on the structurefunction relationships in a bacterial 2H enzyme, which can be used to understand the common and divergent properties of enzymes in the entire 2H superfamily.