Ecdysone protein

Table 3. Comparison of phenoloxldase activity, protein, and ascorbic acid levels In the molt fluid and ascorbic acid levels In the hemoljanph approximately 36 hr following apolysls to the 5th Instar. B. moxn. larvae were Injected per os at 4th Instar 2nd day with 10 pi 30X aq/EtOH alone or with 10 jjl 30X aq/EtOH + phyto-ecdysone 25 larvae were used/treatment/parameter and analyzed.

Diacylhydrazine insecticides (tebufenozide, methoxyfenozide, halofenozide, and chroma-fenozide) act as nonsteroidal ecdysone agonists. They bind to specific ecdysteroid receptorbinding proteins, interrupting the normal sequence of events. Consequently, they induce an incomplete precocious molt, resulting in the mortality of the larva. 

The ecdysone receptor belongs to the same subfamily of nuclear receptors as the liver X receptor LXR, the famesoid X receptor FXR and the vitamin D receptor VDR [8,[48]. All these receptors bind steroid-related compounds (oxysterol, bile acids and vitamin D). A detailed sequence alignment and a phylogenetic analysis encompassing 19 EcR protein sequences of various arthropods has been perfcxmed by Bonneton et al [46]. We will summarize here the main issues of this study. 

Both nuclear receptors EcR and USP that form the functional receptor for ecdysone seem to have evolved in a concerted way during insect evolution. The evolutionary conserved divergences in the protein sequences of arthropod USPs-RXRs and EcRs are... 

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. 

Quinone causes tanning and hardening of the larval cuticle, which is a precondition of moulting. This process, known as sclerotisation, is a result of the reaction between the quinone and the cuticle proteins. One of the basic steps of quinone formation is the decarboxylation of DOPA into dopamine, effected by DOPA decarboxylase. Presumably, the messenger-RNA responsible for DOPA decarboxylase synthesis is formed by the action of ecdysone. 

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... 

Figure 3 shows an example of protein treatment with deuterated solvent for H/D exchange. The bovine albumin digest (Figure 3A) was treated directly on the MALDI sample plate as described above and a second spectrum was acquired (Figure 3B). Results of the PMF identification on the first spectrum querying the SWISS-PROT and TrEMBL databases for mammalian species allowed the identification of bovine albumin (ALBU BOVIN, P02769) at the first rank and Yellow mealworm ecdysone receptor (002035). In the case of bovine albumin, 10 peaks out of 22 were matched in both spectra (Table 7).

Fig. 2. Mechanism of the action of ecdysone. The hormone activates the genetic material to puff up and produce RNA. It is believed that the latter acts as messenger-RNA it enters the cytoplasm and becomes attached to the ribosomes, where it participates in the synthesis of specific proteins.

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