View source for 1nqg


==OUTER MEMBRANE COBALAMIN TRANSPORTER (BTUB) FROM E. COLI, WITH BOUND CALCIUM==
<StructureSection load='1nqg' size='340' side='right'caption='[[1nqg]], [[Resolution|resolution]] 3.31&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1nqg]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NQG OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1NQG FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 3.31&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=C8E:(HYDROXYETHYLOXY)TRI(ETHYLOXY)OCTANE'>C8E</scene>, <scene name='pdbligand=CA:CALCIUM+ION'>CA</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1nqg FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1nqg OCA], [https://pdbe.org/1nqg PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1nqg RCSB], [https://www.ebi.ac.uk/pdbsum/1nqg PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1nqg ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/BTUB_ECOLI BTUB_ECOLI] Involved in the active translocation of vitamin B12 (cyanocobalamin) across the outer membrane to the periplasmic space. It derives its energy for transport by interacting with the trans-periplasmic membrane protein TonB. Is also a receptor for bacteriophages BF23 and C1, and for A and E colicins.[HAMAP-Rule:MF_01531]
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/nq/1nqg_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=1nqg ConSurf].
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== Publication Abstract from PubMed ==
The outer membranes of Gram-negative bacteria possess transport proteins essential for uptake of scarce nutrients. In TonB-dependent transporters, a conserved sequence of seven residues, the Ton box, faces the periplasm and interacts with the inner membrane TonB protein to energize an active transport cycle. A critical mechanistic step is the structural change in the Ton box of the transporter upon substrate binding; this essential transmembrane signaling event increases the affinity of the transporter for TonB and enables active transport to proceed. We have solved crystal structures of BtuB, the outer membrane cobalamin transporter from Escherichia coli, in the absence and presence of cyanocobalamin (vitamin B(12)). In these structures, the Ton box is ordered and undergoes a conformational change in the presence of bound substrate. Calcium has been implicated as a necessary factor for the high-affinity binding (K(d) approximately 0.3 nM) of cyanocobalamin to BtuB. We observe two bound calcium ions that order three extracellular loops of BtuB, thus providing a direct (and unusual) structural role for calcium.

Substrate-induced transmembrane signaling in the cobalamin transporter BtuB.,Chimento DP, Mohanty AK, Kadner RJ, Wiener MC Nat Struct Biol. 2003 May;10(5):394-401. PMID:12652322<ref>PMID:12652322</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 1nqg" style="background-color:#fffaf0;"></div>

==See Also==
*[[BtuB 3D structures|BtuB 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Escherichia coli]]
[[Category: Large Structures]]
[[Category: Chimento DP]]
[[Category: Kadner RJ]]
[[Category: Mohanty AK]]
[[Category: Wiener MC]]