Acts as a Mg(2+) transporter. Can also transport other divalent cations such as Fe(2+), Sr(2+), Ba(2+), Mn(2+) and Co(2+) but to a much less extent than Mg(2+). Homodimer. Recruited to the cell membrane in response to low extracellular magnesium. Widely expressed. Predominantly expressed in neuronal tissues. Brain, heart, kidney, liver and colon (at protein level). Up-regulated by low magnesium ion levels. Belongs to the NIPA family.