A mechanism for indirect allosteric action of charged effectors.

A mechanism for indirect allosteric action of charged effectors on substrate binding to a macromolecule is proposed. It is accounted for by electrostatic interaction among effectors in the solution, away from their receptors. The possibility of the mechanism proposed is tested in the allosteric action of univalent salt and 2,3-diphosphoglycerate on oxygen binding to hemoglobin. A model for electrostatic interaction between these two effectors in the solution and for their overall effect on oxygen binding is introduced. The 2,3-diphosphoglycerate binding constant to deoxygenated hemoglobin as a function of univalent salt concentration and the median ligand activity as a function of the concentration of univalent salt and 2,3-diphoshoglycerate are calculated and compared with experimental data. The obtained results indicate that electrostatic interaction in the solution may significantly contribute to indirect allosteric action of charged effectors.