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  • 1
    Publication Date: 2000-10-20
    Description: Membrane channel proteins of the aquaporin family are highly selective for permeation of specific small molecules, with absolute exclusion of ions and charged solutes and without dissipation of the electrochemical potential across the cell membrane. We report the crystal structure of the Escherichia coli glycerol facilitator (GlpF) with its primary permeant substrate glycerol at 2.2 angstrom resolution. Glycerol molecules line up in an amphipathic channel in single file. In the narrow selectivity filter of the channel the glycerol alkyl backbone is wedged against a hydrophobic corner, and successive hydroxyl groups form hydrogen bonds with a pair of acceptor, and donor atoms. Two conserved aspartic acid-proline-alanine motifs form a key interface between two gene-duplicated segments that each encode three-and-one-half membrane-spanning helices around the channel. This structure elucidates the mechanism of selective permeability for linear carbohydrates and suggests how ions and water are excluded.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fu, D -- Libson, A -- Miercke, L J -- Weitzman, C -- Nollert, P -- Krucinski, J -- Stroud, R M -- GM24485/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2000 Oct 20;290(5491):481-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Biophysics, School of Medicine, University of California, San Francisco, CA 94143-0448, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11039922" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Motifs ; Amino Acid Sequence ; Aquaporins/chemistry/metabolism ; *Bacterial Outer Membrane Proteins/*chemistry/metabolism ; Cell Membrane Permeability ; Conserved Sequence ; Crystallography, X-Ray ; Escherichia coli/*chemistry ; *Escherichia coli Proteins ; Glycerol/chemistry/*metabolism ; Hydrogen Bonding ; Models, Molecular ; Molecular Sequence Data ; Protein Conformation ; Protein Folding ; Protein Structure, Secondary ; Proteolipids/metabolism ; Stereoisomerism ; Sugar Alcohols/metabolism ; Water/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2004-09-14
    Description: The first structure of an ammonia channel from the Amt/MEP/Rh protein superfamily, determined to 1.35 angstrom resolution, shows it to be a channel that spans the membrane 11 times. Two structurally similar halves span the membrane with opposite polarity. Structures with and without ammonia or methyl ammonia show a vestibule that recruits NH4+/NH3, a binding site for NH4+, and a 20 angstrom-long hydrophobic channel that lowers the NH4+ pKa to below 6 and conducts NH3. Favorable interactions for NH3 are seen within the channel and use conserved histidines. Reconstitution of AmtB into vesicles shows that AmtB conducts uncharged NH3.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Khademi, Shahram -- O'Connell, Joseph 3rd -- Remis, Jonathan -- Robles-Colmenares, Yaneth -- Miercke, Larry J W -- Stroud, Robert M -- GM24485/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2004 Sep 10;305(5690):1587-94.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Biophysics, S412C Genentech Hall, University of California-San Francisco, 600 16th Street, San Francisco, CA 94143-2240, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15361618" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Ammonia/*metabolism ; Binding Sites ; Biological Transport ; Cation Transport Proteins/*chemistry/genetics/metabolism ; Cell Membrane/chemistry ; Crystallization ; Crystallography, X-Ray ; Escherichia coli/*chemistry/metabolism ; Escherichia coli Proteins/*chemistry/genetics/metabolism ; Hydrogen Bonding ; Hydrogen-Ion Concentration ; Hydrophobic and Hydrophilic Interactions ; Liposomes ; Membrane Potentials ; Models, Molecular ; Molecular Sequence Data ; Protein Conformation ; Protein Folding ; Protein Structure, Quaternary ; Protein Structure, Secondary ; Quaternary Ammonium Compounds/metabolism ; Rh-Hr Blood-Group System/chemistry/metabolism ; Sequence Alignment ; Water/chemistry/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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