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Updated: May 3, 2026

Identifying the Binding Proteins of Small Ligands with the Differential Radial Capillary Action of Ligand Assay DRaCALA
Published on: March 19, 2021
Fine-tuned broad binding capability of human lipocalin-type prostaglandin D synthase for various small lipophilic
Satoshi Kume1, Young-Ho Lee2, Masatoshi Nakatsuji3
1Laboratory of Biological Macromolecules, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan; Cellular Function Imaging Team, Division of Bio-function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3, Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.
Abstract:
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.
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