SUR belongs to the ABC protein superfamily, a group of
transmembrane proteins that use ATP to transport a large variety
of substrates across extra- and intracellular membranes,
including metabolic products, lipids and sterols, and drugs.
Multidrug-resistant proteins (MRPs) represent a subfamily of
ABC transporters involved in the cellular export of several
drugs, including anthracyclines and vinca alkaloids [21].