title: Kinetics and mechanism for the conformational transition in p-guanidinobenzoate bovine trypsinogen induced by the isoleucine-valine dipeptide.
abstract: The interaction between p-guanidinobenzoate-trypsinogen and the isoleucine-valine dipeptide has been investigated by temperature-jump relaxation spectrometry. Using the absorbance at 281 nm the concentration dependence of the relaxation parameters is consistent with the conventional induced-fit model: rapid ligand binding coupled to a slower intramolecular change; some alternative mechanisms can be excluded. At 296 K, 0.1 M Tris HCl, pH = 7.4, the dissociation equilibrium constant for the overall process is K = 5.1(+/- 0.2) X 10(-5) M; for the binding step K1 = 2.3(+/- 0.3) X 10(-3) M and the rate constants for the structural change are k2 = 26(+/-6)s-1 and k-2 = 0.61(+/- 0.04)s-1; the overall dissociation reaction enthalpy is delta H0 = 26(+/-6)KJmol-1 and the reactiom entropy is delta S0 = 4(+/- 20) kJ-1 mol-1. In combination with CD and X-ray crystallographic data, the results of this study suggest that the binding of the dipeptide to a trypsinogen-like, partially disordered conformation induces a transition to a trypsin-like highly ordered structure.
mesh_terms: D000818:Animals; D001565:Benzoates; D002417:Cattle; D004151:Dipeptides; D006146:Guanidines; D007532:Isoleucine; D007700:Kinetics; D008433:Mathematics; D011485:Protein Binding; D011487:Protein Conformation; D014362:Trypsinogen; D014633:Valine
chemical_list: D001565:Benzoates; D004151:Dipeptides; D006146:Guanidines; D007532:Isoleucine; C023856:4-guanidinobenzoate; D014362:Trypsinogen; D014633:Valine