Structural analysis of the manganese transport regulator MntR from Bacillus halodurans in apo and manganese bound forms

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.

Metagenomic and Metatranscriptomic Study of Microbial Metal Resistance in an Acidic Pit Lake

“…Expression of the Mn transport regulator mntR in the deep layer is consistent with higher Mn concentrations at this depth. The mntR genes are transcriptional repressors that regulate the metal uptake expression by sensing the concentration of Mn(II) [69]. In Escherichia coli, mntR represses mntH (Mn importer) and positively regulates mntP (Mn exporter) [79].…”

AsIII Selectively Induces a Disorder-to-Order Transition in the Metalloid Binding Region of the AfArsR Protein

“…Indeed, careful comparison of crystal structures of the metal-free and metal-bound forms of various metalloregulators (relying partly on modeled structures using AlphaFold 87,88 (Uniprot id: B7J952 (AfArsR), P0ACS5 (ZntR)) and I-TASSER 89−91 (I-TASSER server)) indicates a certain level of flexibility in the metal-free or repressor forms near the effector binding site (Figure S20). Similarly, structural data on the DtxR/MntR family member proteins MntR 92,93 and ScaR, 94 the MerR family sensors CueR, 95,96 ZntR, 95 and MeR, 97 the tetrameric NikR, 98 as well as the ArsR/SmtB family sensory proteins CzrA, 99 CadC, 100,101 and AfArsR 25 all show that the coordinating ligands are only partially arranged in the absence of metal ions. However, metal ion binding reorganizes the coordinating donor groups as well as the surrounding protein skeleton in a way that allows the metal ion to adopt its favored coordination geometry.…”

Regulation and distinct physiological roles of manganese in bacteria

“…Crystal structures of B. halodurans MntR revealed that three instead of the previously assumed two Mn 2+ molecules are bound in the active dimerized molecule (Lee et al . 2019 ). B. subtilis mntR deletion mutants constitutively express both mntH and mntABC , which increases sensitivity to Mn 2+ (as well as to Cd 2+ ) and causes Mn 2+ intoxication (Que and Helmann 2002 ; Huang et al .…”