Ligand-induced thermostability in proteins: thermodynamic analysis of ANS-albumin interaction.
A comparative thermodynamic study of the interaction of anilinonaphthalene sulfonate (ANS) derivatives with bovine serum albumin (BSA) was performed by using differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC). The chemically related ligands, 1,8-ANS and 2,6-ANS, present a similar affinity for BSA with different binding energetics. The analysis of the binding driving forces suggests that not only hydrophobic effect but also electrostatic interactions are relevant, even though they have been extensively used as probes for non-polar domains in proteins. Ligand association leads to an increase in protein thermostability, indicating that both dyes interact mainly with native BSA. ITC data show that 1,8-ANS and 2,6-ANS have a moderate affinity for BSA, with an association constant of around 1-9x10(5) M(-1) for the high-affinity site. Ligand binding is disfavoured by conformational entropy. The theoretical model used to simulate DSC data satisfactorily reproduces experimental thermograms, validating this approach as one which provides new insights into the interaction between one or more ligands with a protein. By comparison with 1,8-ANS, 2,6-ANS appears as a more "inert" probe to assess processes which involve conformational changes in proteins.
Departamento de Química Biológica-CIQUIBIC, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, 5000, Córdoba, Argentina.
M Soledad
MS
Celej
Sergio A
SA
Dassie
Eleonora
E
Freire
M Lucia
ML
Bianconi
Gerardo D
GD
Fidelio
D000817:Anilino Naphthalenesulfonates / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002152:Calorimetry, Differential Scanning; D002417:Cattle; D006358:Hot Temperature; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D011485:Protein Binding / Q000187:drug effects; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism*; D013816:Thermodynamics
D000817:Anilino Naphthalenesulfonates; D008024:Ligands; D012710:Serum Albumin, Bovine