RECOMBINANT HUMAN RETINOIC ACID RECEPTOR-BETA - BINDING OF SYNTHETIC RETINOIDS AND TRANSCRIPTIONAL ACTIVATION

All-trans-retinoic acid mediates cell growth and differentiation by bi nding to and then activating nuclear retinoid receptor proteins that r egulate gene transcription. Recombinant human retinoic acid receptor b eta was cloned and expressed in Escherichia coli as a fusion protein r MBP-RAR beta with maltose-binding protein to facilitate purification. After isolation from bacterial lysates, rMBP-RAR beta was used for bin ding with selected retinoids. Scatchard analysis with [11,12-H-3(2)]al l-trans-retinoic acid gave a K-d of 0.34 nM. Competitive binding studi es with a series of conformationally restricted aromatic retinoids ind icated that the K-i values for binding to rMBP-RAR beta correlated wit h the logs of the EC(50) values for gene transcriptional activation (p less than or equal to 0.05) and with those for the relative activatio n compared to that of all-trans-retinoic acid (p less than or equal to 0.01). Inspection of binding-activation correlation diagrams indicate s candidate structures for improved retinoid agonists or antagonists.