title: Structural basis for gating mechanisms of a eukaryotic P-glycoprotein homolog.
abstract: P-glycoprotein is an ATP-binding cassette multidrug transporter that actively transports chemically diverse substrates across the lipid bilayer. The precise molecular mechanism underlying transport is not fully understood. Here, we present crystal structures of a eukaryotic P-glycoprotein homolog, CmABCB1 from Cyanidioschyzon merolae, in two forms: unbound at 2.6-Å resolution and bound to a unique allosteric inhibitor at 2.4-Å resolution. The inhibitor clamps the transmembrane helices from the outside, fixing the CmABCB1 structure in an inward-open conformation similar to the unbound structure, confirming that an outward-opening motion is required for ATP hydrolysis cycle. These structures, along with site-directed mutagenesis and transporter activity measurements, reveal the detailed architecture of the transporter, including a gate that opens to extracellular side and two gates that open to intramembranous region and the cytosolic side. We propose that the motion of the nucleotide-binding domain drives those gating apparatuses via two short intracellular helices, IH1 and IH2, and two transmembrane helices, TM2 and TM5.
authors.affiliation: Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kodan
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Toru
authors.initials: T
authors.lastname: Nakatsu
authors.forename: Keita
authors.initials: K
authors.lastname: Sakiyama
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hipolito
authors.forename: Akane
authors.initials: A
authors.lastname: Fujioka
authors.forename: Ryo
authors.initials: R
authors.lastname: Hirokane
authors.forename: Keiji
authors.initials: K
authors.lastname: Ikeguchi
authors.forename: Bunta
authors.initials: B
authors.lastname: Watanabe
authors.forename: Jun
authors.initials: J
authors.lastname: Hiratake
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Kimura
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Suga
authors.forename: Kazumitsu
authors.initials: K
authors.lastname: Ueda
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kato
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry*; D000255:Adenosine Triphosphate / Q000378:metabolism; D003461:Crystallography; D055808:Drug Discovery / Q000379:methods*; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology*; D008958:Models, Molecular; D009369:Neoplasms / Q000188:drug therapy*; D010843:Pichia; D011487:Protein Conformation; D000461:Rhodophyta / Q000737:chemistry*; D012441:Saccharomyces cerevisiae; D014961:X-Ray Diffraction
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000255:Adenosine Triphosphate
keywords: ABC transporter; X-ray crystallography; macrocyclic peptide; membrane protein; multidrug resistance