title: Three-dimensional structures of the mammalian multidrug resistance P-glycoprotein demonstrate major conformational changes in the transmembrane domains upon nucleotide binding.
abstract: P-glycoprotein is an ATP-binding cassette transporter that is associated with multidrug resistance and the failure of chemotherapy in human patients. We have previously shown, based on two-dimensional projection maps, that P-glycoprotein undergoes conformational changes upon binding of nucleotide to the intracellular nucleotide binding domains. Here we present the three-dimensional structures of P-glycoprotein in the presence and absence of nucleotide, at a resolution limit of approximately 2 nm, determined by electron crystallography of negatively stained crystals. The data reveal a major reorganization of the transmembrane domains throughout the entire depth of the membrane upon binding of nucleotide. In the absence of nucleotide, the two transmembrane domains form a single barrel 5-6 nm in diameter and about 5 nm deep with a central pore that is open to the extracellular surface and spans much of the membrane depth. Upon binding nucleotide, the transmembrane domains reorganize into three compact domains that are each 2-3 nm in diameter and 5-6 nm deep. This reorganization opens the central pore along its length in a manner that could allow access of hydrophobic drugs (transport substrates) directly from the lipid bilayer to the central pore of the transporter.
authors.affiliation: Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, United Kingdom.
authors.forename: Mark F
authors.initials: MF
authors.lastname: Rosenberg
authors.forename: Alhaji Bukar
authors.initials: AB
authors.lastname: Kamis
authors.forename: Richard
authors.initials: R
authors.lastname: Callaghan
authors.forename: Christopher F
authors.initials: CF
authors.lastname: Higgins
authors.forename: Robert C
authors.initials: RC
authors.lastname: Ford
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D018360:Crystallography, X-Ray; D011487:Protein Conformation
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000255:Adenosine Triphosphate