Mg2+ homeostasis and avoidance of metal toxicity

Mol Microbiol. 2002 Apr;44(2):561-71. doi: 10.1046/j.1365-2958.2002.02917.x.


Because Mg2+ is required for a wide variety of cellular functions, its intracellular levels must be tightly regulated. In the Gram-negative bacterium Salmonella enterica, three transporters mediate Mg2+ uptake: the P-type ATPases MgtA and MgtB, whose expression is transcriptionally induced in low Mg2+ by the Mg2+-regulated PhoP/PhoQ two-component system; and CorA, whose transcription is regulated neither by the levels of Mg2+ nor by the PhoP/PhoQ system. We now report that mutants defective in phoP or in both mgtA and mgtB are hypersensitive to oxidative stress-dependent Fe (II)-mediated killing. These mutants display increased iron accumulation and heightened Ni2+ uptake. Inactivation of the corA gene restored Fe(II) resistance to the phoP mutant and eliminated uptake of Ni2+. Neither corA transcription nor CorA protein levels were altered in the phoP mutant, suggesting that CorA alters its activity in response to the presence of PhoP-regulated determinants. Downregulation of CorA activity in low Mg2+ environments may enable Salmonella to avoid the uncontrolled influx of toxic metals.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Ascorbic Acid / pharmacology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Biological Transport
  • Ca(2+) Mg(2+)-ATPase / genetics
  • Ca(2+) Mg(2+)-ATPase / metabolism*
  • Carrier Proteins / metabolism
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Cations, Divalent / metabolism
  • Gene Expression Regulation, Enzymologic
  • Homeostasis
  • Iron / toxicity
  • Magnesium / metabolism*
  • Magnesium / toxicity
  • Mutagenesis
  • Nickel / metabolism
  • Nickel / toxicity
  • Oxidative Stress / drug effects
  • Oxidative Stress / physiology*
  • Salmonella enterica / drug effects
  • Salmonella enterica / genetics*


  • Bacterial Proteins
  • Carrier Proteins
  • Cation Transport Proteins
  • Cations, Divalent
  • CorA protein, Salmonella
  • PhoP protein, Bacteria
  • Nickel
  • Iron
  • Ca(2+) Mg(2+)-ATPase
  • Magnesium
  • Ascorbic Acid