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  • 1
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    Mechanism of substrate recognition and transport by an amino acid antiporter (2010)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2010-01-22
    Description: In extremely acidic environments, enteric bacteria such as Escherichia coli rely on the amino acid antiporter AdiC to expel protons by exchanging intracellular agmatine (Agm(2+)) for extracellular arginine (Arg(+)). AdiC is a representative member of the amino acid-polyamine-organocation (APC) superfamily of membrane transporters. The structure of substrate-free AdiC revealed a homodimeric assembly, with each protomer containing 12 transmembrane segments and existing in an outward-open conformation. The overall folding of AdiC is similar to that of the Na(+)-coupled symporters. Despite these advances, it remains unclear how the substrate (arginine or agmatine) is recognized and transported by AdiC. Here we report the crystal structure of an E. coli AdiC variant bound to Arg at 3.0 A resolution. The positively charged Arg is enclosed in an acidic binding chamber, with the head groups of Arg hydrogen-bonded to main chain atoms of AdiC and the aliphatic portion of Arg stacked by hydrophobic side chains of highly conserved residues. Arg binding induces pronounced structural rearrangement in transmembrane helix 6 (TM6) and, to a lesser extent, TM2 and TM10, resulting in an occluded conformation. Structural analysis identified three potential gates, involving four aromatic residues and Glu 208, which may work in concert to differentially regulate the upload and release of Arg and Agm.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gao, Xiang -- Zhou, Lijun -- Jiao, Xuyao -- Lu, Feiran -- Yan, Chuangye -- Zeng, Xin -- Wang, Jiawei -- Shi, Yigong -- England -- Nature. 2010 Feb 11;463(7282):828-32. doi: 10.1038/nature08741. Epub 2010 Jan 20.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Ministry of Education Protein Science Laboratory, Tsinghua University, Beijing 100084, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20090677" target="_blank"〉PubMed〈/a〉
    Keywords: Agmatine/metabolism ; Amino Acid Transport Systems/*chemistry/*metabolism ; Antiporters/*chemistry/*metabolism ; Arginine/chemistry/*metabolism ; Biological Transport ; Conserved Sequence ; Crystallography, X-Ray ; Escherichia coli Proteins/*chemistry/*metabolism ; Hydrogen Bonding ; Hydrogen-Ion Concentration ; Hydrophobic and Hydrophilic Interactions ; Protein Conformation ; Protein Folding ; Protein Multimerization ; Protons ; Static Electricity ; Structure-Activity Relationship ; Substrate Specificity
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Structure of a fucose transporter in an outward-open conformation (2010)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2010-09-30
    Description: The major facilitator superfamily (MFS) transporters are an ancient and widespread family of secondary active transporters. In Escherichia coli, the uptake of l-fucose, a source of carbon for microorganisms, is mediated by an MFS proton symporter, FucP. Despite intensive study of the MFS transporters, atomic structure information is only available on three proteins and the outward-open conformation has yet to be captured. Here we report the crystal structure of FucP at 3.1 A resolution, which shows that it contains an outward-open, amphipathic cavity. The similarly folded amino and carboxyl domains of FucP have contrasting surface features along the transport path, with negative electrostatic potential on the N domain and hydrophobic surface on the C domain. FucP only contains two acidic residues along the transport path, Asp 46 and Glu 135, which can undergo cycles of protonation and deprotonation. Their essential role in active transport is supported by both in vivo and in vitro experiments. Structure-based biochemical analyses provide insights into energy coupling, substrate recognition and the transport mechanism of FucP.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dang, Shangyu -- Sun, Linfeng -- Huang, Yongjian -- Lu, Feiran -- Liu, Yufeng -- Gong, Haipeng -- Wang, Jiawei -- Yan, Nieng -- England -- Nature. 2010 Oct 7;467(7316):734-8. doi: 10.1038/nature09406. Epub 2010 Sep 26.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉State Key Laboratory of Bio-membrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20877283" target="_blank"〉PubMed〈/a〉
    Keywords: Crystallography, X-Ray ; Escherichia coli/*chemistry ; Escherichia coli Proteins/*chemistry/metabolism ; Fucose/metabolism ; Hydrophobic and Hydrophilic Interactions ; Models, Biological ; Models, Molecular ; Monosaccharide Transport Proteins/*chemistry/metabolism ; Protein Conformation ; Protons ; Rotation ; Static Electricity ; Symporters/*chemistry/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Structure and mechanism of the uracil transporter UraA (2011)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2011-03-23
    Description: The nucleobase/ascorbate transporter (NAT) proteins, also known as nucleobase/cation symporter 2 (NCS2) proteins, are responsible for the uptake of nucleobases in all kingdoms of life and for the transport of vitamin C in mammals. Despite functional characterization of the NAT family members in bacteria, fungi and mammals, detailed structural information remains unavailable. Here we report the crystal structure of a representative NAT protein, the Escherichia coli uracil/H(+) symporter UraA, in complex with uracil at a resolution of 2.8 A. UraA has a novel structural fold, with 14 transmembrane segments (TMs) divided into two inverted repeats. A pair of antiparallel beta-strands is located between TM3 and TM10 and has an important role in structural organization and substrate recognition. The structure is spatially arranged into a core domain and a gate domain. Uracil, located at the interface between the two domains, is coordinated mainly by residues from the core domain. Structural analysis suggests that alternating access of the substrate may be achieved through conformational changes of the gate domain.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lu, Feiran -- Li, Shuo -- Jiang, Yang -- Jiang, Jing -- Fan, He -- Lu, Guifeng -- Deng, Dong -- Dang, Shangyu -- Zhang, Xu -- Wang, Jiawei -- Yan, Nieng -- England -- Nature. 2011 Apr 14;472(7342):243-6. doi: 10.1038/nature09885. Epub 2011 Mar 20.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉State Key Laboratory of Bio-membrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21423164" target="_blank"〉PubMed〈/a〉
    Keywords: Biological Transport ; Crystallography, X-Ray ; Escherichia coli/*chemistry ; Escherichia coli Proteins/*chemistry/*metabolism ; Hydrogen Bonding ; Membrane Transport Proteins/*chemistry/*metabolism ; Models, Biological ; Models, Molecular ; Protein Folding ; Protein Structure, Secondary ; Protein Structure, Tertiary ; Protons ; Structure-Activity Relationship ; Uracil/chemistry/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray absorption studies on organo-disulfide redox cathodes
    Amsterdam : Elsevier
    Electrochimica Acta 37 (1992), S. 1635-1637 
    Details
    ISSN: 0013-4686
    Keywords: X-ray absorption ; energy storage ; organo-disulfide ; polymeric electrode
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0013-4686(92)80127-8
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