title: Substrate-bound structure of the E. coli multidrug resistance transporter MdfA.
abstract: Multidrug resistance is a serious threat to public health. Proton motive force-driven antiporters from the major facilitator superfamily (MFS) constitute a major group of multidrug-resistance transporters. Currently, no reports on crystal structures of MFS antiporters in complex with their substrates exist. The E. coli MdfA transporter is a well-studied model system for biochemical analyses of multidrug-resistance MFS antiporters. Here, we report three crystal structures of MdfA-ligand complexes at resolutions up to 2.0 Å, all in the inward-facing conformation. The substrate-binding site sits proximal to the conserved acidic residue, D34. Our mutagenesis studies support the structural observations of the substrate-binding mode and the notion that D34 responds to substrate binding by adjusting its protonation status. Taken together, our data unveil the substrate-binding mode of MFS antiporters and suggest a mechanism of transport via this group of transporters.
authors.affiliation: National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Heng
authors.affiliation: National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.|School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: College of Biotechnology, Tianjin University of Science and Technology, 29 13th Street, TEDA, Tianjin 300457, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Liu
authors.affiliation: National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Liu
authors.affiliation: National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Junping
authors.initials: J
authors.lastname: Fan
authors.affiliation: National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Xianping
authors.initials: X
authors.lastname: Wang
authors.affiliation: National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Yongfang
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Xuejun C
authors.initials: XC
authors.lastname: Zhang
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D018432:Drug Resistance, Multiple; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016296:Mutagenesis; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D013379:Substrate Specificity
chemical_list: D029968:Escherichia coli Proteins; D008024:Ligands; C118438:Mdfa protein, E coli; D026901:Membrane Transport Proteins; D011994:Recombinant Proteins