Doxorubicin-efflux pump in Haloferax vokanii is energized by ATP

Haloferax uolcanii acquires resistance to doxorubicin, and this acquisition involves an active extrusion of lipophilic drugs. We have investigated what this drug-efflux transporter utilizes as an energy source to expel drugs from the cells. The efflux activity was estimated from the direct measurement of drug efflux rate and from the steady-state level of drug accumulation. Cells treated with NJ’-dicyclohexyl-carbodiimide showed a significant decrease in the efflux activity without changing membrane potential and Naf-electrochemical potential. This efflux system is energized by ATP but not by either a H+or Naf-electrochemical potential difference.