title: Effectory site in Escherichia coli inorganic pyrophosphatase is revealed upon mutation at the intertrimeric interface.
abstract: Escherichia coli inorganic pyrophosphatase (E-PPase) is a homohexamer formed from two trimers related by a two-fold axis. The residue Asp26 participates in intertrimeric contacts. Kinetics of MgPPi hydrolysis by a mutant Asp26Ala E-PPase is found to not obey Michaelis-Menten equation but can be described within the scheme of activation of hydrolysis by a free PPi binding at an effectory subsite. Existence of such a subsite is confirmed by the finding that the free form of methylenediphosphonate activates MgPPi hydrolysis though its magnesium complex is a competitive inhibitor. The Asp26Ala variant is the first example of hexameric E-PPase demonstrated to have an activatory subsite.
authors.affiliation: Chemistry Department, Moscow State University, Leninskie Gory, 119992 GSP-2, Moscow, Russia.
authors.forename: Tatyana S
authors.initials: TS
authors.lastname: Sitnik
authors.forename: Julia P
authors.initials: JP
authors.lastname: Vainonen
authors.forename: Elena V
authors.initials: EV
authors.lastname: Rodina
authors.forename: Tatyana I
authors.initials: TI
authors.lastname: Nazarova
authors.forename: Svetlana A
authors.initials: SA
authors.lastname: Kurilova
authors.forename: Natalya N
authors.initials: NN
authors.lastname: Vorobyeva
authors.forename: Svetlana M
authors.initials: SM
authors.lastname: Avaeva
mesh_terms: D000409:Alanine / Q000378:metabolism; D001216:Asparagine / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D011756:Diphosphates / Q000378:metabolism; D004164:Diphosphonates / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D043564:Inorganic Pyrophosphatase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D015394:Molecular Structure; D009154:Mutation; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D011756:Diphosphates; D004164:Diphosphonates; D021122:Protein Subunits; D001216:Asparagine; C027474:methylene diphosphonate; D043564:Inorganic Pyrophosphatase; D008274:Magnesium; D000409:Alanine