Protonation and pK changes in protein-ligand binding.

Area of Science:

• Biochemistry
• Computational Biology
• Structural Biology

Background:

• Protein-ligand complex formation induces significant changes in the ionization states of amino acid residues.
• Understanding these alterations in pK values and protonation states is crucial for comprehending molecular interactions.

Purpose of the Study:

• To review the physical origins, computational prediction methods, and impact of pK and protonation state changes during protein-ligand binding.
• To analyze the prevalence, magnitude, and distribution of these ionization changes.
• To explore the pH-dependence of binding and its implications for drug design.

Main Methods:

• Review of experimental and theoretical studies on protein-ligand binding.
• Discussion of computational approaches for predicting pK and protonation state shifts.
• Analysis of statistical data on the prevalence and location of ionization changes.

Main Results:

• Ionization state changes upon binding are common but not universal, varying by complex and methodology.
• These changes can extend beyond the immediate binding interface.
• Binding affinity is often pH-dependent, with a tendency for minimal ionization changes at physiologically relevant pH.

Conclusions:

• Accounting for protonation state changes is essential for accurate modeling of protein-ligand interactions and binding affinities.
• Native interactions may have evolved to minimize ionization energy costs at physiological pH.
• Improved prediction of these changes can enhance structure-based drug design outcomes.