Solution structure of LXXLL-related cofactor peptide of orphan nuclear receptor FTZ-F1

Functional interaction between Drosophila orphan receptor FTZ-F1 (NR5A3) and a segmentation gene product fushi tarazu (FTZ) is crucial for regulating genes related to define the identities of alternate segmental regions in the Drosophila embryo. FTZ binding to the ligand-binding domain (LBD) of FTZ-F1 is of essence in activating its transcription process. We determined solution structures of the cofactor peptide (FTZ^PEP) derived from FTZ by NMR spectroscopy. The cofactor peptide showed a nascent helical conformation in aqueous solution, however, the helicity was increased in the presence of TFE. Furthermore, FTZ^PEP formed α-helical conformation upon FTZ-F1 binding, which provides a receptor bound structure of FTZ^PEP. The solution structure of FTZ^PEP in the presence of FTZ-F1 displays a long stretch of the α-helix with a bend in the middle of helix.