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Drosophila nuclear receptor E75 is a thiolate hemoprotein
Eve de Rosny1, Arjan de Groot, Celine Jullian-Binard
1CEA, CNRS, UJF, UMR 5075, Institut de Biologie Structurale Jean-Pierre Ebel, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France. eve.derosny@ibs.fr
Biochemistry
|August 9, 2006
Summary
Drosophila E75 nuclear receptors bind heme, acting as gas-responsive transcription factors. Researchers identified specific cysteine and histidine residues critical for heme iron coordination in E75.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Nuclear receptors are crucial eukaryotic transcription factors regulating physiological processes.
- The E75 protein, a nuclear receptor, was recently found to bind a heme prosthetic group and respond to gases.
- The specific heme iron ligands in E75 remained uncharacterized.
Purpose of the Study:
- To characterize and assign the heme iron axial ligands in the Drosophila E75 ligand-binding domain (LBD).
- To investigate the role of specific amino acid residues in heme binding and coordination.
Main Methods:
- Site-directed mutagenesis was employed to alter specific amino acid residues in E75.
- UV-visible and electron paramagnetic resonance (EPR) spectroscopies were used to analyze heme binding.
- Protein expression in Escherichia coli with hemin supplementation facilitated heme enrichment.
Main Results:
- Mutations involving cysteines 396 and 468 demonstrated their essential role in heme binding.
- Histidine 574 was identified as the sixth iron ligand in a major coordination conformation.
- EPR studies indicated the presence of iron-bound thiolates, suggesting a thiolate hemoprotein.
Conclusions:
- Drosophila E75 is a novel thiolate hemoprotein.
- The identified ligands (cysteines and histidine) are crucial for E75's heme coordination.
- E75 may play a role in regulating hormone synthesis.