Structural role of a detergent molecule in retinoic acid nuclear receptor crystals

The human nuclear receptor of retinoic acid hRARγ is a ligand-dependent transcription regulator. The presence of a completely ordered dodecyl-α-D-maltoside molecule in the crystal structure of the hRARγ ligand-binding domain (LBD) refined at 1.3 Å resolution is reported. The non-ionic detergent is required for stabilization and crystallization of the hRARγ LBD and mediates a crystal contact in the region where coactivator proteins bind. Its dodecyl moiety is buried in a hydrophobic channel, whereas the maltoside head group is hydrogen bonded to water molecules and polar residue side chains.