title: A new structural model for P-glycoprotein.
abstract: Multidrug resistance to anti-cancer drugs is a major medical problem. Resistance is manifested largely by the product of the human MDR1 gene, P-glycoprotein, an ABC transporter that is an integral membrane protein of 1280 amino acids arranged into two homologous halves, each comprising 6 putative transmembrane alpha-helices and an ATP binding domain. Despite the plethora of data from site-directed, scanning and domain replacement mutagenesis, epitope mapping and photoaffinity labeling, a clear structural model for P-glycoprotein remains largely elusive. In this report, we propose a new model for P-glycoprotein that is supported by the vast body of previous data. The model comprises 2 membrane-embedded 16-strand beta-barrels, attached by short loops to two 6-helix bundles beneath each barrel. Each ATP binding domain contributes 2 beta-strands and 1 alpha-helix to the structure. This model, together with an analysis of the amino acid sequence alignment of P-glycoprotein isoforms, is used to delineate drug binding and translocation sites. We show that the locations of these sites are consistent with mutational, kinetic and labeling data.
authors.affiliation: Department of Cell and Molecular Biology, University of Technology Sydney, Sydney, NSW 2007, Australia.
authors.forename: P M
authors.initials: PM
authors.lastname: Jones
authors.forename: A M
authors.initials: AM
authors.lastname: George
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry* / Q000235:genetics; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D019450:Genes, MDR; D006801:Humans; D051379:Mice; D008854:Microscopy, Electron; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry*; D017433:Protein Structure, Secondary; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013055:Spectrophotometry, Infrared; D013329:Structure-Activity Relationship
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D020033:Protein Isoforms; D000255:Adenosine Triphosphate