Protein interactions with small molecules. Relationships between stoichiometric binding constants, site binding...

Area of Science:

• Biochemistry
• Chemical Physics

Background:

• Macromolecule-ligand binding is fundamental in biological processes.
• Understanding binding equilibria is complex due to multiple sites and interactions.

Purpose of the Study:

• To develop a unified framework for analyzing macromolecule-ligand binding equilibria.
• To provide a method for distinguishing between stoichiometric and site-specific binding constants.
• To enable the analysis of binding in systems with complex interactions and conformational changes.

Main Methods:

• Formulation of binding equilibria using stoichiometric and site-oriented analyses.
• Derivation of equations relating stoichiometric binding constants (Ki) to site binding constants (kj).
• Development of a graphical procedure plotting iKi against i to generate an affinity profile.

Main Results:

• Demonstrated that stoichiometric binding constants (Ki) can always describe binding dependence on ligand concentration.
• Showed that site binding constants (kj) require defining 2n-1 independent constants in the general case.
• Introduced a graphical affinity profile for visualizing binding constants and detecting site interactions.

Conclusions:

• The derived equations facilitate the definition and analysis of binding in systems with interactions and conformational accommodations.
• The graphical affinity profile offers a concise representation of binding magnitudes and interaction effects.
• This approach enhances the understanding of molecular recognition and binding dynamics.