Abstract
The manganese transport regulator MntR is a metal-ion activated transcriptional repressor of manganese transporter genes to maintain manganese ion homeostasis. MntR, a member of the diphtheria toxin repressor (DtxR) family of metalloregulators, selectively responds to Mn2+ and Cd2+ over Fe2+, Co2+ and Zn2+. The DtxR/MntR family members are well conserved transcriptional repressors that regulate the expression of metal ion uptake genes by sensing the metal ion concentration. MntR functions as a homo-dimer with one metal ion binding site per subunit. Each MntR subunit contains two domains: an N-terminal DNA binding domain, and a C-terminal dimerization domain. However, it lacks the C-terminal SH3-like domain of DtxR/IdeR. The metal ion binding site of MntR is located at the interface of the two domains, whereas the DtxR/IdeR subunit contains two metal ion binding sites, the primary and ancillary sites, separated by 9 Å. In this paper, we reported the crystal structures of the apo and Mn2+-bound forms of MntR from Bacillus halodurans, and analyze the structural basis of the metal ion binding site. The crystal structure of the Mn2+-bound form is almost identical to the apo form of MntR. In the Mn2+-bound structure, one subunit contains a binuclear cluster of manganese ions, the A and C sites, but the other subunit forms a mononuclear complex. Structural data about MntR from B. halodurans supports the previous hypothesizes about manganese-specific activation mechanism of MntR homologues.
Highlights
Metal ions are essential for living organisms because iron, zinc, and manganese ions act as cofactors for many proteins which are involved in photosynthesis, nerve transmission, and defense against toxins[1]
The apo crystal structure of BhMntR was determined at 2.3 Å resolution using molecular replacement with the manganese transport regulator (MntR) model of B. subtilis (2HYG)
We reported the crystal structures of BhMntR: apo, and Mn2+-bound forms
Summary
Metal ions are essential for living organisms because iron, zinc, and manganese ions act as cofactors for many proteins which are involved in photosynthesis, nerve transmission, and defense against toxins[1]. Manganese ions are important in many fundamental cellular processes, including protection against oxidative stress and the synthesis of the deoxyribonucleotides required for DNA replication[2,3]. Excess of manganese ions can be toxic [4,5]. Bank (PDB): apo BhMntR, PDB ID, 6KTA; Mn2+ -bound BhMntR, PDB ID, 6KTB
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