Na(+)/H(+) antiporter that extrudes sodium in exchange for external protons. 2 H(+)(out) + Na(+)(in) = 2 H(+)(in) + Na(+)(out) Belongs to the NhaA Na(+)/H(+) (TC 2.A.33) antiporter family. The sequence is interrupted by the insertion of an IS4 element between positions 304 and 305.