ABC (ATP-binding cassette) transporters share a common architecture comprising two variable hydrophobic transmembrane domains (TMDs) that form the translocation pathway and two conserved hydrophilic ABC-ATPases that hydrolyze ATP. This is the C-terminal regulatory domain found at the ATPase subunit of CysA, a putative sulfate ABC transporter from Alicyclobacillus acidocaldarius. The regulatory domain of CysA is built up of an elongated beta-barrel composed of two beta-sandwiches that form a common hydrophobic core [1].

1: Structure of the ATPase subunit CysA of the putative sulfate ATP-binding cassette (ABC) transporter from Alicyclobacillus acidocaldarius. Scheffel F, Demmer U, Warkentin E, Hulsmann A, Schneider E, Ermler U; FEBS Lett. 2005;579:2953-2958. PMID:15893314