The structures of Escherichia coli inorganic pyrophosphatase complexed with Ca(2+) or CaPP(i) at atomic resolution and their mechanistic implicationsстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Two structures of Escherichia coli soluble inorganic pyrophosphatase (EPPase) complexed with calcium pyrophosphate (CaPPi-EPPase) and with Ca2+ (Ca2+-EPPase) have been solved at resolution 1.2 and 1.1 Å, respectively. This enzyme cleaves pyrophosphate (PPi) into two molecules of orthophosphate (Pi) in the presence of Mg2+. This work has enabled to locate PPi in the active site of the inorganic pyrophosphatases family in the presence of Ca2+ which is an inhibitor of EPPase. Upon PPi binding two Ca2+ at M1 and M2 subsites move closer together so that one of liganded water molecules becomes bridging. The mutual location of PPi and the bridging water molecule in the presence of inhibitor cation is catalytically incompetent. To make favourable PPi attack by this water molecule, modelling of a possible hydrolysable conformation of PPi in CaPPi-EPPase active site has been performed. The reasons of Ca2+ being the strong PPases inhibitor and the role in catalysis of each of four metal ions are the mechanistic aspects discussed on the basis of described structures.