Mechanism of drug transport by ABC multidrug proteins in structural perspectives

ABC (ATP Binding Cassette) proteins form one of the largest protein superfamilies. Most members are active membrane transporters translocating their substrates across the lipid bilayer of the plasma membrane or intracellular organelles. Multidrug transporters exhibit broad substrate specificity, exporting molecules with diverse chemical structures to protect organisms from xenotoxic compounds, and also play an important role in influencing the efficacy of therapeutic agents. High resolution structural information is required to reveal the conformational changes associated with the transport cycle and the interaction with small molecules, with the ultimate aim to develop strategies to pharmacologically modulate function and predict substrates properties. In this chapter we review available ABC protein structures and discuss advances in using this structural information for computational approaches that are aimed at elucidating the mechanism of substrate recognition and cargo translocation in the context of the ATP catalytic cycle of human multidrug ABC transporters.