Structural insights into the molecular mechanism of ABC transporters

ABC (ATP-binding cassette) transporters mediate the translocation of a large variety of molecules across lipid bilayers and are directly driven by energy from ATP hydrolysis. Since the first crystal structure of an ABC transporter, the E. coli vitamin B12 transporter BtuCD, was reported in 2002, over thirty structures of ABC proteins in different functional states have been determined by X-ray crystallography or by single particle cryo-electron microscopy reconstruction. In this review, structural details of ABC transporters, the maltose transporter of Escherichia coli and the P-glycoprotein of Caenorhabditis elegans, are discussed to understand the molecular mechanism of ABC importers and exporters, respectively.