LIGAND-BINDING PROPERTIES OF HUMAN CELLULAR RETINOIC ACID-BINDING PROTEIN-II EXPRESSED IN ESCHERICHIA-COLI AS A GLUTATHIONE-S-TRANSFERASE FUSION PROTEIN

To test the hypothesis that 9-cis-retinoic acid is a ligand for cellular retinoic acid binding protein II (CRABP II), human CRABP II 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 bound all trans-retinoic acid with high affinity (K(d) 14.2 +/- 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.