Na(+)/H(+) antiporter that extrudes sodium in exchange for external protons. Has also weak Li(+)/H(+) antiport activity. Inhibited by amiloride. Optimum pH is 7.5. Almost no activity is detected below pH 7.0 or above pH 8.5. Belongs to the monovalent cation:proton antiporter 1 (CPA1) transporter (TC 2.A.36) family.