Na(+)/H(+) antiporter that imports sodium into the cell in exchange for protons. Can also transport lithium. May be involved in adaptation to marine habitats. Induced by hyperosmotic shock. Belongs to the NhaD Na(+)/H(+) (TC 2.A.62) antiporter family. It is uncertain whether Met-1 or Met-72 is the initiator. Truncated N-terminus.