title: The role of strong electrostatic interactions at the dimer interface of human glutathione synthetase.
abstract: The obligate homodimer human glutathione synthetase (hGS) provides an ideal system for exploring the role of protein-protein interactions in the structural stability, activity and allostery of enzymes. The two active sites of hGS, which are 40 Å apart, display allosteric modulation by the substrate γ-glutamylcysteine (γ-GC) during the synthesis of glutathione, a key cellular antioxidant. The two subunits interact at a relatively small dimer interface dominated by electrostatic interactions between S42, R221, and D24. Alanine scans of these sites result in enzymes with decreased activity, altered γ-GC affinity, and decreased thermal stability. Molecular dynamics simulations indicate these mutations disrupt interchain bonding and impact the tertiary structure of hGS. While the ionic hydrogen bonds and salt bridges between S42, R221, and D24 do not mediate allosteric communication in hGS, these interactions have a dramatic impact on the activity and structural stability of the enzyme.
authors: Department of Chemistry and Biochemistry, Texas Woman's University, P.O. Box 425859, Denton, TX, 76204, USA.
authors: Margarita C
authors: MC
authors: De Jesus
authors: Brandall L
authors: BL
authors: Ingle
authors: Khaldoon A
authors: KA
authors: Barakat
authors: Bisesh
authors: B
authors: Shrestha
authors: Kerri D
authors: KD
authors: Slavens
authors: Thomas R
authors: TR
authors: Cundari
authors: Mary E
authors: ME
authors: Anderson
mesh_terms: D003460:Crystallization; D019281:Dimerization; D004795:Enzyme Stability; D005981:Glutathione Synthase / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism*; D055672:Static Electricity
chemical_list: D021122:Protein Subunits; D005981:Glutathione Synthase