title: Thermodynamics of the folding of D-glyceraldehyde-3-phosphate dehydrogenase assisted by protein disulfide isomerase studied by microcalorimetry.
abstract: Thermodynamics of the refolding of denatured D-glyceraldehyde 3-phosphate dehydrogenase (GAPDH) assisted by protein disulfide isomerase (PDI), a molecular chaperone, has been studied by isothermal microcalorimetry at different molar ratios of PDI/GAPDH and temperatures using two thermodynamic models proposed for chaperone-substrate binding and chaperone-assisted substrate folding, respectively. The binding of GAPDH folding intermediates to PDI is driven by a large favorable enthalpy decrease with a large unfavorable entropy reduction, and shows strong enthalpy-entropy compensation and weak temperature dependence of Gibbs free energy change. A large negative heat-capacity change of the binding, -156 kJ.mol(-1).K(-1), at all temperatures examined indicates that hydrophobic interaction is a major force for the binding. The binding stoichiometry shows one dimeric GAPDH intermediate per PDI monomer. The refolding of GAPDH assisted by PDI is a largely exothermic reaction at 15.0-25.0 degrees C. With increasing temperature from 15.0 to 37.0 degrees C, the PDI-assisted reactivation yield of denatured GAPDH upon dilution decreases. At 37.0 degrees C, the spontaneous reactivation, PDI-assisted reactivation and intrinsic molar enthalpy change during the PDI-assisted refolding of GAPDH are not detected.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Beijing, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Liang
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: C C
authors.initials: CC
authors.lastname: Wang
mesh_terms: D000818:Animals; D002151:Calorimetry / Q000379:methods*; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D019277:Entropy; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000737:chemistry*; D006358:Hot Temperature; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D018832:Molecular Chaperones / Q000378:metabolism; D019704:Protein Disulfide-Isomerases / Q000737:chemistry*; D017510:Protein Folding; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D018832:Molecular Chaperones; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D019704:Protein Disulfide-Isomerases