title: Evidence for a Sav1866-like architecture for the human multidrug transporter P-glycoprotein.
abstract: The recently reported structures of the bacterial multidrug exporter Sav1866 suggest a domain architecture in which both nucleotide-binding domains (NBDs) of this ATP binding cassette (ABC) transporter contact both transmembrane domains (TMDs). Such a domain arrangement is particularly unexpected because it is not found in the structures of three solute importers BtuCD, HI1470/1, and ModBC from the same protein family. There is also no precedent for such an arrangement from biochemical studies with any ABC transporter. Sav1866 is homologous with the clinically relevant human P-glycoprotein (ABCB1). If the structure proposed for Sav1866 is physiologically relevant, the long intracellular loops of P-glycoprotein TMD2 should contact NBD1. We have tested this by using cysteine mutagenesis and chemical cross-linking to verify proximal relationships of the introduced sulfhydryls across the proposed interdomain interface. We report the first biochemical evidence in support of the domain arrangement proposed for the multidrug resistance class of ABC transporters. With a domain arrangement distinctly different from the three solute importers it seems likely that the TMDs of ABC importers and exporters have evolved different mechanisms to couple to common conformational changes at conserved NBDs.
authors.affiliation: MRC Clinical Sciences Centre, Imperial College, Hammersmith Hospital Campus, Du Cane Rd., London W12 0NN, UK.
authors.forename: Joseph K
authors.initials: JK
authors.lastname: Zolnerciks
authors.forename: Carol
authors.initials: C
authors.lastname: Wooding
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Linton
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D003545:Cysteine / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D006193:Haemophilus influenzae / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D040681:Structural Homology, Protein
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; C050021:BtuC peptide, E coli; C050022:BtuD peptide, E coli; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D009711:Nucleotides; D003545:Cysteine