The magnesium transporter A is activated by cardiolipin and is highly sensitive to free magnesium in vitro

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Abstract

The magnesium transporter A (MgtA) is a specialized P-type ATPase, believed to import Mg²⁺ into the cytoplasm. In Salmonella typhimurium and Escherichia coli, the virulence determining two-component system PhoQ/PhoP regulates the transcription of mgtA gene by sensing Mg²⁺ concentrations in the periplasm. However, the factors that affect MgtA function are not known. This study demonstrates, for the first time, that MgtA is highly dependent on anionic phospholipids and in particular, cardiolipin. Colocalization studies confirm that MgtA is found in the cardiolipin lipid rafts in the membrane. We further show that MgtA is highly sensitive to free Mg²⁺ (Mg²⁺_free) levels in the solution. MgtA is activated when the Mg²⁺_free concentration is reduced below 10 μM and is strongly inhibited above 1 mM, indicating that Mg²⁺_free acts as product inhibitor. Combined, our findings conclude that MgtA may act as a sensor as well as a transporter of Mg²⁺.

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Saranya Subramani

Norwegian Centre of Molecular Medicine, Nordic EMBL Partnership University of Oslo, Oslo, Norway

Competing interests
The authors declare that no competing interests exist.
Harmonie Perdreau-Dahl

Norwegian Centre of Molecular Medicine, Nordic EMBL Partnership University of Oslo, Oslo, Norway

Competing interests
The authors declare that no competing interests exist.
Jens Preben Morth

Norwegian Centre of Molecular Medicine, Nordic EMBL Partnership University of Oslo, Oslo, Norway

For correspondence
j.p.morth@ncmm.uio.no

Competing interests
The authors declare that no competing interests exist.

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