An electrogenic sodium-translocating ATPase in Methanococcus voltae

A membrane potential negative inside generated by the electrogenic efflux K + via valinomycin was demonstrated to be a driving force for the synthesis of ATP in Methanococcus voltae, but only in the presence of sodium. ATP synthesis was prevented by the addition of external potassium or of the sodium ionophore monensin, but was not inhibited by the protonophore SF6847. ATP synthesis in the absence of potassium in the medium could also be driven by a chemical concentration gradient of sodium directed inwards, but only in the presence of a permeant counterion (tetraphenylborate). These results show that M. voltae contains an electrogenic ATP-driven ion pump which translocates sodium.