Complex sentence: Mutations in the ATPase domain result in loss of transport function and the activity of the multidrug transporter in drug-resistant cells is associated with rapid cellular ATP depletion when ATP synthesis is inhibited.
Split into simpler sentences: Mutations in the ATPase domain result in loss of transport function. The activity of the multidrug transporter in drug-resistant cells is associated with rapid cellular ATP depletion when ATP synthesis is inhibited.