May 1, 1990
Journal name not available for this finding
The finely-tuned regulation of biological activity in processes such as development, differentiation, and growth is most often mediated by not one macromolecule, but by relatively large complexes involving several interacting species. Such macro-molecular assemblies include multisubunit proteins and enzymes, complexes of proteins with nucleic acids and protein membrane assemblies. The activity (enzymatic, transport, or binding) of these complexes is often modulated by small effectors such as ions, protons, sugars, etc. A detailed understanding of the underlying mechanisms of such regulation necessitates the determination of the free energy linkages between the various binding equilibria. While the ligand binding equilibria in such systems have been extensively studied, the interactions between the macromolecules themselves have not in general been well characterized. Since the subunit affinities involved in such systems range from 10-11 to 10-5 M, a combination of fluorescence spectroscopy and high hydrostatic pressure is necessary to observe these subunit dissociation reactions at equilibrium. Results of such studies on a number of oligomeric protein systems are reviewed and a new approach to the analysis of such data is proposed.