Evaluation of ligand induced relative change in the bimolecular quenching constant of protein fluorescence: applications to lysozyme and adenosine deaminase.

Abstract

By using our model, described in the preceding paper, we investigate the effect of tri-N-acetylglucosamine binding on lysozyme. Furthermore, we reprocess the recently published data (Biochemistry, 1985, 24, 1342) on the effect of different inhibitors on adenosine deaminase. For lysozyme, the inhibitor binding decreases the dynamic accessibility of Trp-108 by changing the dynamics of the protein region separating the buried Trp-108 from the solvent. The reprocessed data on adenosine deaminase-inhibitor systems indicate that the inhibitors which presumably stabilize different (ground or transient) states alter the protein dynamics in both a qualitatively and quantitatively different manner in good agreement with the thermodynamic data of inhibitor binding. Our approach allows us to conclude that ligand induced changes of protein dynamics are not uniform and usually depend on where the protein-ligand complex is situated along the reaction coordinate (or phase-space) and are not localized to the protein groups building up the binding center.