Ultraspiracle protein

Publication of the crystal structure of the Hdiothis viresence EcR (HvEcR) LBD heterodimerized with LBD of H. viresence ultraspiracle protein (HvUSP) with and without ponasterone A (phytoecdysteroid) or a BAH ecdysone agonist provided a more realistic conformation of the HvEcR LBD and the ligands in the LBD [21]. The most surprising result was that ponasterone A co-crystallized in the HvEcR LBD in an orientation opposite to that predicted by the CoMEA, 4D-QSAR and... 

Secretion of ecdysone starts the many biochemical processes that are necessary for the molting. The cells in the epidermis are stimulated to produce a new cuticle, and when ready, the insect will creep out of its old skin. The molecular mechanism of ecdysone has been studied in some detail. The molecular target of ecdysone and other ecdysteroids consists of at least two proteins, the ecdysteroid receptor (EcR) and ultraspiracle (USP). Both EcR and USP are members of the steroid hormone receptor superfamily with characteristic ligand-binding domains. An EcR-USP-ecdysteroid complex is formed, which activates several genes that code for transcription factors, i.e., proteins that activate or repress the activity of other genes, and the appropriate amounts of proteases and other enzymes necessary to degrade old structures and rebuild new ones are formed in a time-controlled sequence. 

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