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The C-terminal domain of the virulence factor MgtC is a divergent ACT domain

Yinshan Yang1, Gilles Labesse, Séverine Carrère-Kremer

  • 1CNRS, UMR 5048, Université Montpellier 1 and Université Montpellier 2, Centre de Biochimie Structurale, Montpellier, France.

Journal of Bacteriology
|September 18, 2012
PubMed

Insights

The Mycobacterium tuberculosis MgtC protein, a virulence factor, does not bind magnesium (Mg2+). Instead, its C-terminal domain facilitates protein interactions, suggesting a regulatory role in bacterial survival.

Area of Science:

  • Microbiology
  • Structural Biology
  • Bacterial Pathogenesis

Background:

  • MgtC is a virulence factor in intracellular bacteria like Mycobacterium tuberculosis, crucial for macrophage survival.
  • MgtC is implicated in adaptation to magnesium (Mg2+) deprivation, but its precise function remains unclear, with prior evidence suggesting it's not a Mg2+ transporter.

Purpose of the Study:

  • To elucidate the functional and structural organization of the MgtC protein from Mycobacterium tuberculosis.
  • To investigate the role of the MgtC C-terminal domain in Mg2+ binding and protein interactions.

Main Methods:

  • Determined the nuclear magnetic resonance (NMR) structure of the C-terminal domain of M. tuberculosis MgtC.
  • Assessed Mg2+ effects on the C-terminal domain structure.
  • Utilized a bacterial two-hybrid system to study MgtC protein dimerization.

Main Results:

  • The M. tuberculosis MgtC protein level is not significantly altered by Mg2+ deprivation.
  • The NMR structure of the MgtC C-terminal domain revealed a βαββαβ fold characteristic of ACT domains but lacking canonical small molecule binding and dimerization capabilities.
  • The MgtC C-terminal domain was found to facilitate MgtC protein dimerization, despite not binding Mg2+.

Conclusions:

  • MgtC from M. tuberculosis does not directly mediate Mg2+ uptake or binding.
  • The MgtC protein likely functions as a regulatory factor through protein-protein interactions, potentially mediated by its ACT domain.
  • The C-terminal domain's role in facilitating dimerization suggests a mechanism for regulating MgtC function within the bacterial cell.

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