Manganese homeostasis in Bacillus subtilis is regulated by MntR, a bifunctional regulator related to the diphtheria toxin repressor family of proteins

Abstract

The Bacillus subtilis yqhN gene encodes a metalloregulatory protein distantly related to the Corynebacterium diphtheriae diphtheria toxin repressor (DtxR). While DtxR mediates the iron‐dependent repression of iron uptake, we demonstrate that yqhN (herein renamed mntR) encodes a manganese modulated regulator of manganese transport. An mntR mutant strain is sensitive to both manganese and cadmium, suggesting that the transport of these metals is derepressed. We selected Tn10 insertions that suppress the Mn(II) sensitivity of the mntR mutant or that increase the Cd(II) tolerance of wild‐type cells, and in both cases we recovered insertions in mntH (formerly ydaR). MntH is a member of the NRAMP family of proton‐coupled, metal ion transporters. MntR also regulates expression of a Mn(II) ABC transporter (MntABCD). The MntH and MntABCD transporters are both selectively repressed by Mn(II) and this regulation requires MntR. In high Mn(II) conditions, MntR functions as a Mn(II)‐dependent repressor of mntH transcription. In contrast, MntR acts as a positive regulator of the mntABCD operon under low Mn(II) growth conditions. Biochemical studies demonstrate that MntR binding to the mntH control region requires Mn(II), while interaction with the mntABCD control region does not depend on Mn(II).

Genome-based in silico detection of putative manganese transport systems in Lactobacillus plantarum and their genetic analysis

“…Similar systems have been identified in Bacillus subtilis (Que & Helmann, 2000), Salmonella typhimurium (Kehres et al, 2000) and E. coli (Makui et al, 2000), and confer highaffinity uptake of Mn 2+ . Molecular studies of the enterobacterial (Kehres et al, 2000) and B. subtilis (Que & Helmann, 2000) nramp genes demonstrated that they encode proton-stimulated, highly selective Mn 2+ transporters that play a role in the bacterial response to oxidative stress (Kehres et al, 2000).…”

Control of bacterial iron homeostasis by manganese

“…Growth of an Escherichia coli iron-transport mutant is inhibited in an mntH background, suggesting that manganese may substitute for iron in cells (6). The mntH and sitABCD genes are transcriptionally regulated by iron as well as by manganese in the model organisms E. coli, Salmonella enterica, and Bacillus subtilis (7)(8)(9). However, a regulatory role for manganese in controlling cellular processes other than its own transport is less well understood, and is addressed in the present study.…”

The Conformations of the Manganese Transport Regulator of Bacillus subtilis in its Metal-free State

“…The weaker binding of the mononuclear MntR•Zn 2+ complex to DNA is likely related to a partial loss of restraints between domains, suggesting a mechanism for the selective activation of MntR by Mn 2+ and Cd 2+ over other competing metal ions. [1][2][3]18,20 Ongoing studies will further explore the conformational and structural changes associated with the activation of MntR to its high-affinity DNA-binding state upon metal binding.…”

“…1 When cellular levels of manganese are high, MntR represses the transcription of genes encoding manganese uptake transporters by binding to cognate operator sequences. [1][2][3] Manganese is an essential nutrient in bacteria and plays an important role in cellular defense 17,18 MntR is a functional homodimer of 142-residue subunits, each composed of two domains. The 71-residue N-terminal DNA-binding domain consists of three α-helices and two strands of antiparallel β-sheet (Figure 1), the latter forming the flexible "wing" of a winged helix-turn-helix (HTH) motif that interacts with DNA.17 , 19 The Cterminal domain contains four α-helices and forms the dimerization interface with its dyadrelated mate.…”