title: Three-dimensional structure of the human breast cancer resistance protein (BCRP/ABCG2) in an inward-facing conformation.
abstract: ABCG2 is an efflux drug transporter that plays an important role in drug resistance and drug disposition. In this study, the first three-dimensional structure of human full-length ABCG2 analysed by electron crystallography from two-dimensional crystals in the absence of nucleotides and transported substrates is reported at 2 nm resolution. In this state, ABCG2 forms a symmetric homodimer with a noncrystallographic twofold axis perpendicular to the two-dimensional crystal plane, as confirmed by subtomogram averaging. This configuration suggests an inward-facing configuration similar to murine ABCB1, with the nucleotide-binding domains (NBDs) widely separated from each other. In the three-dimensional map, densities representing the long cytoplasmic extensions from the transmembrane domains that connect the NBDs are clearly visible. The structural data have allowed the atomic model of ABCG2 to be refined, in which the two arms of the V-shaped ABCG2 homodimeric complex are in a more closed and narrower conformation. The structural data and the refined model of ABCG2 are compatible with the biochemical analysis of the previously published mutagenesis studies, providing novel insight into the structure and function of the transporter.
authors.affiliation: Faculty of Life Science, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, England.
authors.forename: Mark F
authors.initials: MF
authors.lastname: Rosenberg
authors.affiliation: Virtua Drug Ltd, Budapest 1015, Hungary.
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Bikadi
authors.affiliation: Faculty of Life Science, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, England.
authors.forename: Eszter
authors.initials: E
authors.lastname: Hazai
authors.affiliation: Faculty of Life Science, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, England.
authors.forename: Tobias
authors.initials: T
authors.lastname: Starborg
authors.affiliation: Centre for Bioinformatics, Division of Molecular Biosciences, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, England.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Kelley
authors.affiliation: Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Sir Alexander Fleming Building, London SW7 2AZ, England.
authors.forename: Naomi E
authors.initials: NE
authors.lastname: Chayen
authors.affiliation: Faculty of Life Science, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, England.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Ford
authors.affiliation: Department of Pharmaceutics, School of Pharmacy, University of Washington, Seattle, WA 98195, USA.
authors.forename: Qingcheng
authors.initials: Q
authors.lastname: Mao
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D001940:Breast / Q000378:metabolism; D001943:Breast Neoplasms / Q000378:metabolism; D020285:Cryoelectron Microscopy / Q000379:methods; D003460:Crystallization / Q000379:methods; D005260:Female; D006801:Humans; D008958:Models, Molecular; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D009363:Neoplasm Proteins
keywords: ABC transporter; ABCG2; ATP-binding cassette transporter; BCRP; cryo-electron microscopy; three-dimensional structure from two-dimensional crystals