A Mg2+-responding RNA that controls the expression of a Mg 2+ transporter

E. A. Groisman, M. J. Cromie, Yixin Shi, T. Latifi

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Mg2+ is the most abundant divalent cation in biological systems. It is required for ATP-mediated enzymatic reactions and as a stabilizer of ribosomes and membranes. The enteric bacterium Salmonella enterica serovar Typhimurium harbors three Mg2+ transporters and a regulatory system-termed PhoP/PhoQ-whose activity is regulated by the extracytoplasmic levels of Mg2+. We have determined that expression of the PhoP-activated Mg2+ transporter MgtA is also controlled by its 5′-untranslated region (5′UTR). The 5′UTR of the mgtA gene can adopt different stem-loop structures depending on the Mg2+ levels, which determine whether transcription reads through into the mgtA-coding region or stops within the 5′UTR. This makes the mgtA 5′UTR the first example of a cation-responding riboswitch. The initiation of mgtA transcription responds to extracytoplasmic Mg2+, and its elongation into the coding region to cytoplasmic Mg2+, which provides a singular example where the same ligand is sensed in different cellular compartments to regulate disparate steps in gene transcription. The PhoP-activated Mg2+ transporter MgtB is also regulated by Mg2+ in a strain lacking the Mg2+ sensor PhoQ, suggesting the presence of additional Mg 2+-responding devices.

Original languageEnglish (US)
Pages (from-to)251-258
Number of pages8
JournalCold Spring Harbor symposia on quantitative biology
StatePublished - 2006

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Genetics


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