ATP-binding cassette domain of an uncharacterized transporter similar in sequence to NatA
NatA is the ATPase component of a bacterial ABC-type Na+ transport system called NatAB, which catalyzes ATP-dependent electrogenic Na+ extrusion without mechanically coupled to proton or K+ uptake. NatB possess six putative membrane spanning regions at its C-terminus. In B. subtilis, NatAB is inducible by agents such as ethanol and protonophores, which lower the proton-motive force across the membrane. The closest sequence similarity to NatA is exhibited by DrrA of the two-component daunorubicin- and doxorubicin-efflux system. Hence, the functional NatAB is presumably assembled with two copies of the single ATP-binding protein and the single integral membrane protein.