title: Engineering a new magnesium binding site in the subunit contact region of Escherichia coli inorganic pyrophosphatase.
abstract: Three Gln-80 residues belonging to different subunits of homohexameric Escherichia coli pyrophosphatase are separated by only one water molecule to which they are hydrogen bonded. Substitution of Glu for Gln-80 stabilizes quaternary structure of the enzyme but has only a small effect on enzyme activity. The substitution stimulates Mg2+ binding and changes the appearance of the Mg2+ concentration dependence of the rate constant for the trimer --> hexamer transition. These data suggest that a new Mg2+ binding site is formed in the intersubunit contact region as a result of the substitution. Three-dimensional modeling of the mutated protein showed that a chelate complex might form involving two of the three Glu-80 residues.
authors.affiliation: Belozersky Institute of Physico-Chemical Biology and School of Chemistry, Lomonosov Moscow State University, Moscow, 119899, Russia.
authors.forename: A N
authors.initials: AN
authors.lastname: Parfenyev
authors.forename: A
authors.initials: A
authors.lastname: Salminen
authors.forename: A A
authors.initials: AA
authors.lastname: Baykov
authors.forename: R
authors.initials: R
authors.lastname: Lahti
mesh_terms: D019943:Amino Acid Substitution; D001665:Binding Sites; D011756:Diphosphates / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005973:Glutamine / Q000378:metabolism; D043564:Inorganic Pyrophosphatase; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011108:Polymers; D015202:Protein Engineering; D011755:Pyrophosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D011756:Diphosphates; D011108:Polymers; D005973:Glutamine; D011755:Pyrophosphatases; D043564:Inorganic Pyrophosphatase; D008274:Magnesium