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The mechanism of Zinc Inhibition of Glutamate Dehydrogenase Involves Disruption of Subunit Interactions
Author(s) -
Sinanan Leander,
Bell Ellis
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.676.11
Subject(s) - isothermal titration calorimetry , zinc , glutamate dehydrogenase , chemistry , proteolysis , biochemistry , protein subunit , biophysics , tryptophan , amino acid , glutamate receptor , stereochemistry , enzyme , biology , organic chemistry , receptor , gene
Zinc is a potent inhibitor of higher eukaryotic glutamate dehydrogenase but the mechanism of inhibition has not been established. The goal of the current study is to correlate zinc binding under various conditions with changes in activity and conformational flexibility. Using Isothermal Titration Calorimetry it is shown that zinc binds to glutamate dehydrogenase with a 1:1 stoichiometry in the presence or absence of amino acid substrates. Using tryptophan fluorescence spectroscopy it appears that zinc affects the most hydrophobic of the three tryptophans in the protein. Examination of the three dimensional structure of the enzyme suggests that zinc may bind at the subunit interface in the "twisty tie" region of the molecule. This is consistent with both the location of the most hydrophobic tryptophan and the fact that zinc appears to inhibit by disrupting subunit interactions necessary for full activity with glutamate as substrate. Differential Scanning Calorimetry and Limited Proteolysis approaches demonstrate that zinc binding induces changes in the conformational flexibility of glutamate dehydrogenase which could be responsible for this effect. This research is supported by a Grant from the National Science Foundation: MCB 0448905 to EB