title: Crystal structure of holo inorganic pyrophosphatase from Escherichia coli at 1.9 A resolution. Mechanism of hydrolysis.
abstract: Crystalline holo inorganic pyrophosphatase from Escherichia coli was grown in the presence of 250 mM MgCl2. The crystal structure has been solved by Patterson search techniques and refined to an R-factor of 17.6% at 1.9 A resolution. The upper estimate of the root-mean-square error in atomic positions is 0.26 A. These crystals belong to space group P3(2)21 with unit cell dimensions a = b = 110.27 A and c = 78.17 A. The asymmetric unit contains a trimer of subunits, i.e., half of the hexameric molecule. In the central cavity of the enzyme molecule, three Mg2+ ions, each shared by two subunits of the hexamer, are found. In the active sites of two crystallographically independent subunits, two Mg2+ ions are bound. The second active site Mg2+ ion is missing in the third subunit. A mechanism of catalysis is proposed whereby a water molecule activated by a Mg2+ ion and Tyr 55 play essential roles.
authors.affiliation: Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federation. emil@protein.crystal.msk.ru
authors.forename: E H
authors.initials: EH
authors.lastname: Harutyunyan
authors.forename: V Y
authors.initials: VY
authors.lastname: Oganessyan
authors.forename: N N
authors.initials: NN
authors.lastname: Oganessyan
authors.forename: S M
authors.initials: SM
authors.lastname: Avaeva
authors.forename: T I
authors.initials: TI
authors.lastname: Nazarova
authors.forename: N N
authors.initials: NN
authors.lastname: Vorobyeva
authors.forename: S A
authors.initials: SA
authors.lastname: Kurilova
authors.forename: R
authors.initials: R
authors.lastname: Huber
authors.forename: T
authors.initials: T
authors.lastname: Mather
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology*; D006868:Hydrolysis; D043564:Inorganic Pyrophosphatase; D008956:Models, Chemical; D011485:Protein Binding; D011755:Pyrophosphatases / Q000737:chemistry*
chemical_list: D011755:Pyrophosphatases; D043564:Inorganic Pyrophosphatase