Na(+)/H(+) antiporter that extrudes sodium in exchange for external protons. Can also use potassium as a coupling ion, without completely replacing H(+). This Na(+)/H(+)-K(+) antiport is much more rapid than Na(+)/H(+) antiport. Can also extrude lithium. Important for the inosine-dependent germination of spores. Disruption causes a major defect in inosine-dependent germination, but does not significantly affect germination in response to L-alanine. Belongs to the monovalent cation:proton antiporter 2 (CPA2) transporter (TC 2.A.37) family.