![]() It was proposed that MgtC might act by sequestering Mg 2+ and/or by facilitating transport by specific transporters. Studies carried out with the Salmonella protein demonstrated that MgtC is not a Mg 2+ transporter ( 15, 26) and led to alternative hypothesis. Moreover, a role for MgtC in Mg 2+ homeostasis is supported by the fact that expression of the mgtC gene is highly induced by deprivation of the external Mg 2+ concentration in S. The role of MgtC in adaptation to Mg 2+ limitation has suggested that MgtC plays a role in Mg 2+ uptake. MgtC has been involved in adaptation to low-Mg 2+ environments in liquid culture media in the various pathogens mentioned above: the growth of mgtC mutants is impaired when the Mg 2+ concentration is low ( 2). Later, it was described as a critical factor for the intramacrophage growth of Mycobacterium tuberculosis, Brucella suis, Yersinia pestis, Burkholderia cenocepacia, and Salmonella enterica serovar Typhi ( 5, 12, 22, 24, 31).ĭespite its importance in virulence of various bacterial pathogens, the biochemical function of MgtC, which is a membrane-associated protein, remains unknown, and members of the MgtC family show only low homology to proteins of known function. ![]() MgtC was first described for Salmonella enterica serovar Typhimurium, where it is required for intramacrophage multiplication and long-term systemic infection in mice ( 3, 23, 36). ![]() MgtC is a virulence factor common to several intracellular pathogens ( 2). tuberculosis MgtC does not have an intrinsic function related to Mg 2+ uptake or binding but could act as a regulatory factor based on protein-protein interaction that could be facilitated by its ACT domain. Taken together, these results indicate that M. tuberculosis MgtC protein can dimerize and that the C-terminal domain somehow facilitates this dimerization. We have shown, using a bacterial two-hybrid system, that the M. tuberculosis MgtC ACT domain differs from canonical ACT domains because it appears to lack the ability to dimerize and to bind small molecules. The structure of the C-terminal domain forms a βαββαβ fold found in small molecule binding domains called ACT domains. This structure is not affected by the Mg 2+ concentration, indicating that it does not bind Mg 2+. To get insights into MgtC functional and structural organization, we have determined the nuclear magnetic resonance (NMR) structure of the C-terminal domain of M. Members of the MgtC protein family share a conserved membrane N-terminal domain and a more divergent cytoplasmic C-terminal domain. tuberculosis MgtC protein is not significantly increased by Mg 2+ deprivation. In this study, we demonstrated that the amount of the M. ![]() It is also involved in adaptation to Mg 2+ deprivation, but previous work suggested that MgtC is not a Mg 2+ transporter. MgtC is a virulence factor of unknown function important for survival inside macrophages in several intracellular bacterial pathogens, including Mycobacterium tuberculosis. ![]()
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