Abstract
IdeR is an iron-dependent repressor protein, one of the essential proteins found in Mycobacterium tuberculosis. IdeR is a homologue of the diphtheria toxin repressor (DtxR). IdeR controls iron acquisition and storage, moreover it binds to DNA and regulates the virulence gene expression. Only Fe(II) can bind and activate IdeR in vivo, however other divalent metals can also activate these proteins in vitro. The IdeR D177K has a hyperactive phenotype in that is has apparently lost the metal sensitivity and permanently represses virulence gene expression. This has sparked interest in identify peptide activators of IdeR of which HR1 has been pursued here. The HR1, is a cationic synthesized peptide, binds IdeR. This peptide is bacteriocidal in iron-depleted medium. HR1 may represent a new class of antibiotics with iron homeostasis, however, the details of this peptide structure and functions are unknown. The overall objectives of this research are to determine conditions suitable for preparation of IdeR-HR1 complex at high concentrations for NMR and crystallization, and also perform crystallization screening trials of HR1 bound IdeR and IdeR M10A, a single mutation at metal site, with Ni(II). Methods for sub-cloning, optimization of protein and peptide purifications are explained, and those are resulted in high expression and purity levels of IdeR. None of trials formed HR1 bound IdeR crystal, however the peptide was crystallized in one conditions.
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