1i40
STRUCTURE OF INORGANIC PYROPHOSPHATASE
OverviewOverview
Two structures of Escherichia coli soluble inorganic pyrophosphatase (EPPase) complexed with calcium pyrophosphate (CaPP(i)-EPPase) and with Ca(2+) (Ca(2+)-EPPase) have been solved at 1.2 and 1.1 A resolution, respectively. In the presence of Mg(2+), this enzyme cleaves pyrophosphate (PP(i)) into two molecules of orthophosphate (P(i)). This work has enabled us to locate PP(i) in the active site of the inorganic pyrophosphatases family in the presence of Ca(2+), which is an inhibitor of EPPase.Upon PP(i) binding, two Ca(2+) at M1 and M2 subsites move closer together and one of the liganded water molecules becomes bridging. The mutual location of PP(i) and the bridging water molecule in the presence of inhibitor cation is catalytically incompetent. To make a favourable PP(i) attack by this water molecule, modelling of a possible hydrolysable conformation of PP(i) in the CaPP(i)-EPPase active site has been performed. The reasons for Ca(2+) being the strong PPase inhibitor and the role in catalysis of each of four metal ions are the mechanistic aspects discussed on the basis of the structures described.
About this StructureAbout this Structure
1I40 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
The structures of Escherichia coli inorganic pyrophosphatase complexed with Ca(2+) or CaPP(i) at atomic resolution and their mechanistic implications., Samygina VR, Popov AN, Rodina EV, Vorobyeva NN, Lamzin VS, Polyakov KM, Kurilova SA, Nazarova TI, Avaeva SM, J Mol Biol. 2001 Nov 30;314(3):633-45. PMID:11846572 Page seeded by OCA on Fri May 2 19:32:44 2008