Ligand binding properties of human cellular retinoic acid binding protein II expressed inE. colias a glutathione‐S‐transferase fusion protein

Abstract
To test the hypothesis that 9‐cis‐retinoic acid is a ligand for cellular retinoic acid binding protein II (CRABPII), human CRABPII was expressed as a glutathione‐S‐transferase fusion protein (GST‐CRABP II) and a single affinity purification step used to extract it from bacterial lysates. GST‐CRABP II boundall trans‐retinoic acid with high affinity (Kd14.2 ± 6.5 nM), but 9‐cis‐retinoic acid bound poorly. These studies suggest that 9‐cis‐retinoic acid is not a ligand for CRABP II. Their ease of purification makes GST‐CRABP fusion proteins useful tools for ligand binding studies with different retinoids.