Magnesium (Mg2+) is required for the catalytic activity of numerous metalloenzymes within a variety of subcellular organelles. Magnesium transporters NIPA1, 2, 3, 4 (NIPA1,2,3,4) and NIPA-like proteins 2 and 2 (NIPAL2 and 3) can act as Mg2+ transporters. They may also transport other divalent cations such as Fe2+, Mn2+ and Ba2+ but to a lesser extent than Mg2+. Human NIPA1 mediates Mg2+ uptake when expressed in Xenopus oocytes (Goytain et al. 2007). The other NIPA members are included as candidates based on NIPA1 function.