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

The human nuclear receptor of retinoic acid hRARgamma is a ligand-dependent transcription regulator. The presence of a completely ordered dodecyl-alpha-D-maltoside molecule in the crystal structure of the hRARgamma ligand-binding domain (LBD) refined at 1. 3 A resolution is reported. The non-ionic detergent is required for stabilization and crystallization of the hRARgamma 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.