RXR Complexes with Unnatural Ligands

One significant difference between these two structures is the position of helix-12 in the complex between RXR-a, BMS-649 and a co-activator peptide, helix-12 is in the standard agonist position. In the complex between LG-268 and RXR-yS helix-12 is in a novel position not seen in other NHR structures. In this position LG-268 does not fold over and cap the ligand. Additional data indicate that LG- 

268 is unable to release co-repressors from RXR unless co-activators are also present this suggests that certain RXR ligands alone may be inefficient at repositioning helix-12 [34]. 

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