title: Energetics of Glutathione Binding to Human Eukaryotic Elongation Factor 1 Gamma: Isothermal Titration Calorimetry and Molecular Dynamics Studies.
abstract: The energetics of ligand binding to human eukaryotic elongation factor 1 gamma (heEF1γ) was investigated using reduced glutathione (GSH), oxidised glutathione (GSSG), glutathione sulfonate and S-hexylglutathione as ligands. The experiments were conducted using isothermal titration calorimetry, and the findings were supported using computational studies. The data show that the binding of these ligands to heEF1γ is enthalpically favourable and entropically driven (except for the binding of GSSG). The full length heEF1γ binds GSSG with lower affinity (Kd= 115 μM), with more hydrogen-bond contacts (ΔH = -73.8 kJ/mol) and unfavourable entropy (-TΔS = 51.7 kJ/mol) compared to the glutathione transferase-like N-terminus domain of heEF1γ, which did not show preference to any specific ligand. Computational free binding energy calculations from the 10 ligand poses show that GSSG and GSH consistently bind heEF1γ, and that both ligands bind at the same site with a folded bioactive conformation. This study reveals the possibility that heEF1γ is a glutathione-binding protein.
authors.affiliation: Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa.
authors.forename: Thabiso N
authors.initials: TN
authors.lastname: Tshabalala
authors.affiliation: Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa.
authors.forename: Mihai-Silviu
authors.initials: MS
authors.lastname: Tomescu
authors.affiliation: School of Chemistry, University of the Witwatersrand, Johannesburg, 2050, South Africa.
authors.forename: Allan
authors.initials: A
authors.lastname: Prior
authors.affiliation: Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa.
authors.forename: Vijayakumar
authors.initials: V
authors.lastname: Balakrishnan
authors.affiliation: Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa.
authors.forename: Yasien
authors.initials: Y
authors.lastname: Sayed
authors.affiliation: Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa.
authors.forename: Heini W
authors.initials: HW
authors.lastname: Dirr
authors.affiliation: Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa. Ikechukwu.Achilonu@wits.ac.za.
authors.forename: Ikechukwu
authors.identifier: http://orcid.org/0000-0002-8658-956X
authors.initials: I
authors.lastname: Achilonu
mesh_terms: D002151:Calorimetry; D015870:Gene Expression; D005978:Glutathione / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D019803:Glutathione Disulfide / Q000737:chemistry* / Q000378:metabolism; D005982:Glutathione Transferase / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006860:Hydrogen Bonding; D007700:Kinetics; D008024:Ligands; D056004:Molecular Dynamics Simulation; D020648:Peptide Elongation Factor 1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D040681:Structural Homology, Protein; D013696:Temperature; D013816:Thermodynamics
chemical_list: D008024:Ligands; D020648:Peptide Elongation Factor 1; D011994:Recombinant Proteins; C000599475:eEF1B-gamma protein, human; C040136:glutathione sulfonate; D005982:Glutathione Transferase; D005978:Glutathione; C033550:hexylglutathione; D019803:Glutathione Disulfide
keywords: CHARMm-docking; Glutathione-binding energetics; Homology modelling; Human eukaryotic elongation factor 1 gamma; Isothermal titration calorimetry; Molecular dynamics simulations