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Structural adaptability in the ligand-binding pocket of the ecdysone hormone receptor


The ecdysteroid hormones coordinate the major stages of insect development, notably moulting and metamorphosis, by binding to the ecdysone receptor (EcR); a ligand-inducible nuclear transcription factor1,2. To bind either ligand or DNA, EcR must form a heterodimer with ultraspiracle (USP), the homologue of retinoid-X receptor3,4,5. Here we report the crystal structures of the ligand-binding domains of the moth Heliothis virescens EcR–USP heterodimer in complex with the ecdysteroid ponasterone A and with a non-steroidal, lepidopteran-specific agonist BYI06830 used in agrochemical pest control. The two structures of EcR–USP emphasize the universality of heterodimerization as a general mechanism common to both vertebrates and invertebrates. Comparison of the EcR structures in complex with steroidal and non-steroidal ligands reveals radically different and only partially overlapping ligand-binding pockets that could not be predicted by molecular modelling and docking studies6,7. These findings offer new perspectives for the design of insect-specific, environmentally safe insecticides. The concept of a ligand-dependent binding pocket in EcR provides an insight into the moulding of nuclear receptors to their ligand, and has potential applications for human nuclear receptors.

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Figure 1: The two structures of the ligand-binding domains of EcR–USP.
Figure 2: The LBDs of EcR complexed to a steroidal and a non-steroidal ligand exhibit different and only partially overlapping ligand-binding cavities.
Figure 3: Two radically different binding modes for EcR.


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We are grateful to G. Holmwood, K. Tietjen and M. Schindler (Bayer CropScience) for providing us with BYI06830 and ponA. We thank H. Greschik, H. Gronemeyer, B. Klaholz and G. Richards for critical comments on the manuscript; Y. Brelivet and J. M. Wurtz for discussion and advice; H. Nierengarten for mass spectrometry analysis; V. Chavant, D. Rose and F. Zink for technical assistance; S. Sasorith for her help with figures; and C. Massobrio for support and encouragement. We thank the staff of the ESRF ID14 beamline (Grenoble, France) and of the French beamline BM30A (Grenoble, France) for assistance during synchrotron data collection. This work was supported by Bayer CropScience and by grants from CNRS, INSERM, the Hôpital Universitaire de Strasbourg, the Ministère de la Recherche et de la Technologie (Programme de Génomique Structurale) and EU-SPINE.

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Correspondence to Dino Moras.

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Supplementary Figure 4: Composed of three panels (a) electrostatic potential surface (b) dose-dependence of the transactivational activity of the wild-type and the quadruple-mutant hvEcR-LBD/hvUSP and (c) electrospray ionization mass-spectra for the wild-type and the quadruple-mutant hvEcR-LBD/hvUSP. (PDF 1611 kb)

Supplementary Figure 5: Sequence alignment of EcR-LBDs with human VDR-LBD. (DOC 34 kb)

Supplementary Table 1: Crystallographic data and the refinement statistics. (DOC 25 kb)

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Billas, I., Iwema, T., Garnier, JM. et al. Structural adaptability in the ligand-binding pocket of the ecdysone hormone receptor. Nature 426, 91–96 (2003).

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