Introduction
ABC transporters are intricate molecular systems that characterize the
vectorial transport of various substrates across biological membranes.
They are present in all extant species ranging from prokaryotes to
humans (Childs & Ling, 1994; Jones & George, 2004) and comprise the
largest family of transmembrane proteins. These transmembrane proteins
bind ATP and utilize the energy to drive the active transport of diverse
molecules across all cell membranes against the concentration gradient
(Dean & Annilo, 2005; Higgins, 1992; KM Moitra, 2012). Characterization
of this important class of transporters, which contain one of the
largest and ancient protein subfamilies that transport a myriad of
substrates from sugars, amino acids, proteins to metal ions, will yield
invaluable insights into the molecular basis and physiology of human
diseases (Higgins, 1992).