Biophysical Society Thematic Meeting - November 16-20, 2015

Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Poster Abstracts

31-POS Board 31 MgtA from E. Coli Show Strong Cardiolipin Dependent Activity and is Stimulated by Free Mg 2+ in the Sub Micromolar Range Saranya Subramani, Harmonie Perdreau-Dahl, Jens Preben Morth . Oslo University, Oslo, Norway. Clusters of virulence genes, called pathogenicity islands, are incorporated into the genome of pathogenic microorganisms. The clusters are normally absent in the non-pathogenic microorganism of the related species. Pathogenicity islands containing genes associated with bacterial pH and magnesium homeostasis have been shown to play a crucial role in bacterial virulence, thus emphasizing the important role of magnesium and acidification of the local environment during bacterial virulence and survival within the host cell. The Magnesium transporter A (MgtA) is a specialized P-type ATPase important for with magnesium import. The gene mgtA is upregulated when low magnesium levels or low pH in the periplasmic space activate the two-component system PhoQ/PhoP. PhoQ/PhoP is linked with virulence in most pathogenic bacteria. These studies demonstrate, for the first time, that MgtA is highly sensitive to free magnesium levels in solution and follow a kinetic model that suggest initial activation at sub micromolar levels by free magnesium (1-10 μM) followed by strong substrate inhibition at elevated magnesium levels, already at 1 mM, indicating that MgtA may act as a cytoplasmic magnesium sensor as well as a transporter. The activity of MgtA is highly dependent on the presence of phosphatidylglycerols (PG) lipids and in particular cardiolipin. Overexpressed MgtA in E. coli furthermore confirm that MgtA co-localize with the cardiolipin/PG lipid rafts in the plasma membrane. In the presence of CL the dependencies between ATP, free Magnesium and pH have been explored over a wide range. MgtA belongs to the P3B –type ATPase subfamily that include members from eubacteria, archaea, fungi and plants.

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