Figure 5. Model illustrating the regulation of Mg2+ uptake by MgtA.
When PhoQ senses low Mg2+free (<50 μM) in periplasm, it phosphorylates PhoP. This activates PhoP and it promotes transcription of the mgtA gene. MgtA protein is targeted to CL-rich region in bacterial inner membrane. Association of MgtA with CL is essential for its activity. MgtA imports Mg2+free available in periplasm to the cytoplasm of bacteria, thereby increasing cytoplasmic Mg2+free concentration. When the cytoplasmic Mg2+free concentration reaches a threshold (~1 mM), MgtA is inhibited both at the transcriptional and the post-translational level.