Sodium ion binding proteins

The present invention relates to the cloning and expression of a sodium ion binding protein. In particular, the invention relates to cloning and expression of a _nS gene. The _nS gene product, NhaS, is a protein characterized by binding to and sequestering sodium ion (Na+). The invention further relates to functional fragments of a sodium ion binding protein, which fragments are characterized by their ability to bind to sodium ion. In a specific embodiment, the fragment is a fragment of NhaS. The gene encoding the sodium binding protein can be introduced into cells to produce desalination bioreactors. The gene encoding the sodium binding protein can also be introduced into plants as a transgene to produce plants that are resistant to sodium. The sodium binding protein itself may be used for treatments involving Na+/K+ ATPase disorders, e.g., in heart disease; the protein also may be introduced parenterally, preferably orally, to bind to and sequester dietary sodium.