tretinoin and 2-(4-toluidino)-6-naphthalenesulfonic-acid

The hydrophobic cavity of lipocalin-type prostaglandin D synthase (L-PGDS) has been suggested to accommodate various lipophilic ligands through hydrophobic effects, but its energetic origin remains unknown. We characterized 18 buffer-independent binding systems between human L-PGDS and lipophilic ligands using isothermal titration calorimetry. Although the classical hydrophobic effect was mostly detected, all complex formations were driven by favorable enthalpic gains. Gibbs energy changes strongly correlated with the number of hydrogen bond acceptors of ligand. Thus, the broad binding capability of L-PGDS for ligands should be viewed as hydrophilic interactions delicately tuned by enthalpy-entropy compensation using combined effects of hydrophilic and hydrophobic interactions.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Amino Acid Substitution; Bilirubin; Biliverdine; Catalytic Domain; Gonadal Hormones; Hemin; Humans; Hydrophobic and Hydrophilic Interactions; Intramolecular Oxidoreductases; Ligands; Lipocalins; Naphthalenesulfonates; Protein Binding; Steroids; Thermodynamics; Thyroid Hormones; Tretinoin