The NIPA4 gene in mice is located on chromosome 11B1.1 and the human corresponding gene, hIchthyin is located on chromosome 5q33.3. Both genes share an 85% amino acid similarity. Interestingly, NIPA2-4 show greater common identity in their ancestral invertebrate polypeptides than they do to NIPA1 suggesting different physiological roles. NIPA4 mediates Mg2+ uptake with a Km of 0.36 mM but unlike NIPA2, which is selective for Mg2+, it has been found to transport other cations as well
