Characterization of a family I inorganic pyrophosphatase from Legionella pneumophila Philadelphia 1

Inorganic pyrophosphate (PP_i) is generated as an intermediate or byproduct of many fundamental metabolic pathways, including DNA/RNA synthesis. The intracellular concentration of PP_i must be regulated as buildup can inhibit many critical cellular processes. Inorganic pyrophosphatases (PPases) hydrolyze PP_i into two orthophosphates (P_i), preventing the toxic accumulation of the PP_i byproduct in cells and making P_i available for use in biosynthetic pathways. Here, the crystal structure of a family I inorganic pyrophosphatase from Legionella pneumophila is reported at 2.0 Å resolution. L. pneumophila PPase (LpPPase) adopts a homohexameric assembly and shares the oligonucleotide/oligosaccharide-binding (OB) β-barrel core fold common to many other bacterial family I PPases. LpPPase demonstrated hydrolytic activity against a general substrate, with Mg²⁺ being the preferred metal cofactor for catalysis. Legionnaires' disease is a severe respiratory infection caused primarily by L. pneumophila, and thus increased characterization of the L. pneumophila proteome is of interest.