Importance of Protonation States for the Binding of Ligands to Pharmaceutical Targets

PODJARNY, ALBERTO; HOWARD, EDUARDO I

Multifaceted Roles of Crystallography in Modern Drug Discovery

Springer Netherlands

Lugar: Dordrecht; Año: 2015; p. 129 - 139

Protonation states of protein residues in ligand binding sites determine the electrostatic potential, which is essential to understand the interactions of the ligand and the protein. The case of aldose reductase is shown as an example. Inhibitors bind to the active site and to the nearby selectivity pocket. The case of two inhibitors, IDD 594 and Fidarestat, is discussed. The binding properties are determined by the protonation states of the protein residues, notably of His 110, and by the protonation state of the ligand, which can change in the case of  Fidarestat. In this latter case the change in the charged state of the ligand during binding, from neutral to negative, combines the advantage of strong potency (charged state) and favorable pharmacokinetics (neutral state).