title: ABCG transporters: structure, substrate specificities and physiological roles : a brief overview.
abstract: The ATP-binding cassette (ABC) transporter superfamily is one of the largest protein families with representatives in all kingdoms of life. Members of this superfamily are involved in a wide variety of transport processes with substrates ranging from small ions to relatively large polypeptides and polysaccharides. The G subfamily of ABC transporters consists of half-transporters, which oligomerise to form the functional transporter. While ABCG1, ABCG4 and ABCG5/8 are involved in the ATP-dependent translocation of steroids and, possibly, other lipids, ABCG2 (also termed the breast cancer resistance protein) has been identified as a multidrug transporter that confers resistance on tumor cells. Evidence will be summarized suggesting that ABCG2 can also mediate the binding/transport of non-drug substrates, including free and conjugated steroids. The characterization of the substrate specificities of ABCG proteins at a molecular level might provide further clues about their potential physiological role(s), and create new opportunities for the modulation of their activities in relation to human disease.
authors.affiliation: Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK.
authors.forename: Saroj
authors.initials: S
authors.lastname: Velamakanni
authors.forename: Shen L
authors.initials: SL
authors.lastname: Wei
authors.forename: Tavan
authors.initials: T
authors.lastname: Janvilisri
authors.forename: Hendrik W
authors.initials: HW
authors.lastname: van Veen
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000502:physiology*; D001692:Biological Transport; D018432:Drug Resistance, Multiple; D005260:Female; D006801:Humans; D008297:Male; D009363:Neoplasm Proteins; D013256:Steroids / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D009363:Neoplasm Proteins; D013256:Steroids