title: Effector-induced dissociation of glyceraldehyde-3-phosphate dehydrogenase discriminated by urea solvation.
abstract: The dissociation of glyceraldehyde-3-phosphate dehydrogenase (GAPD) from pig muscle in water solutions (0.1 M phosphate, pH 7) at increased urea concentrations was studied by means of frontal-gel chromatography, intrinsic (TRP) fluorescence, differential absorption spectroscopy and selective chemical modification at TRP0193. The results are in agreement with a consecutive two-step model of dissociation of the tetramer and the dimer (C*T = 0.42 M urea < C*D = 1.39 M urea). The binding effector(s) destabilizes the oligomeric structures (delta GT changes from -1.00 to -0.54 kcal/mol; delta GD from -2.30 to -1.22 kcal/mol). The introduction of the bulky Koshland-reagent group to TRP-193 at the subunit-subunit interface leads to a decrease of the stability with delta delta G approximate to 1 kcal/mol, owing to TRP-193...TYR-39...TYR-92 cluster destruction. By using lobster GAPD atomic coordinates (PDB file 1GPD) and pig muscle GAPD amino-acid sequence, a tentative molecular model was constructed and the subunit contacts in terms of the Lee-Richard static accessibilities were described. A detailed analysis of the dissociation as a transfer of the buried residues from the molecular interface to the urea solutions was performed.
authors.affiliation: Biophysical Chemistry of Proteins Laboratory, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors.forename: V
authors.initials: V
authors.lastname: Ivanova
authors.forename: N
authors.initials: N
authors.lastname: Krusteva
authors.forename: B
authors.initials: B
authors.lastname: Atanasov
mesh_terms: D000818:Animals; D001665:Binding Sites; D002850:Chromatography, Gel; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000737:chemistry / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology*; D008121:Nephropidae; D013050:Spectrometry, Fluorescence; D013054:Spectrophotometry, Atomic; D013552:Swine; D013816:Thermodynamics; D014508:Urea
chemical_list: D014508:Urea; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases