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2izk

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[[Image:2izk.gif|left|200px]]<br /><applet load="2izk" size="350" color="white" frame="true" align="right" spinBox="true"
 
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caption="2izk, resolution 1.3&Aring;" />
 
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'''STREPTAVIDIN-GLYCOLURIL PH 2.58 I4122 COMPLEX'''<br />
 
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==Overview==
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==STREPTAVIDIN-GLYCOLURIL PH 2.58 I4122 COMPLEX==
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The remarkable stability of the streptavidin tetramer towards subunit dissociation becomes even greater upon binding of biotin. At two equivalent extensive monomer-monomer interfaces, monomers tightly associate into dimers that in turn associate into the tetramer at a less extensive dimer-dimer interface. To probe the structural basis for the enhancement of the stability of streptavidin by biotin, the crystal structures of apostreptavidin and its complexes with biotin and other small molecule and cyclic peptide ligands were determined and compared at resolutions as high as 1.36 A over a range of pH values from as low as 1.39. At low pH dramatic changes occur in the conformation and intersubunit hydrogen bonds involving the loop comprising Asp61 to Ser69. The hydrogen-bonded salt bridge between Asp61 Odelta2 and His87 Ndelta1, observed at higher pH, is replaced with a strong hydrogen bond between Asp61 Odelta1 and Asn85 Odelta1. Through crystallography at multiple pH values, the pH where this conformational change occurs, and thus the pKa of Asp61, was determined in crystals of space group I222 and/or I4122 of apostreptavidin and complexes. A range in pKa values for Asp61 was observed in these structures, the lowest being 1.78+/-0.19 for I222 streptavidin-biotin in 2.9 M (NH4)2SO4. At low pH the decrease in pKa of Asp61 and preservation of the intersubunit Asp61 Odelta2-Ndelta1 His87 hydrogen-bonded salt bridge in streptavidin-biotin versus apostreptavidin or streptavidin-peptide complexes is associated with an ordering of the flexible flap comprising residues Ala46 to Glu51, that in turn orders the Arg84 side-chain of a neighboring loop through resulting hydrogen bonds. Ordering of Arg84 in close proximity to the strong intersubunit interface appears to stabilize the conformation associated with the Asp61 Odelta2-Ndelta1 His87 hydrogen-bonded salt bridge. Thus, in addition to the established role of biotin in tetramer stabilization by direct mediation of intersubunit interactions at the weak interface through contact with Trp120, biotin may enhance tetramer stability at the strong interface more indirectly by ordering loop residues.
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<StructureSection load='2izk' size='340' side='right'caption='[[2izk]], [[Resolution|resolution]] 1.30&Aring;' scene=''>
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== Structural highlights ==
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<table><tr><td colspan='2'>[[2izk]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Streptomyces_avidinii Streptomyces avidinii]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2IZK OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2IZK FirstGlance]. <br>
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</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.3&#8491;</td></tr>
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<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ACT:ACETATE+ION'>ACT</scene>, <scene name='pdbligand=GLL:GLYCOLURIL'>GLL</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene></td></tr>
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<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=2izk FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2izk OCA], [https://pdbe.org/2izk PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2izk RCSB], [https://www.ebi.ac.uk/pdbsum/2izk PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2izk ProSAT]</span></td></tr>
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</table>
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== Function ==
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[https://www.uniprot.org/uniprot/SAV_STRAV SAV_STRAV] The biological function of streptavidin is not known. Forms a strong non-covalent specific complex with biotin (one molecule of biotin per subunit of streptavidin).
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== Evolutionary Conservation ==
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[[Image:Consurf_key_small.gif|200px|right]]
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Check<jmol>
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<jmolCheckbox>
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<scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/iz/2izk_consurf.spt"</scriptWhenChecked>
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<scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
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<text>to colour the structure by Evolutionary Conservation</text>
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</jmolCheckbox>
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</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=2izk ConSurf].
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<div style="clear:both"></div>
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==About this Structure==
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==See Also==
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2IZK is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Streptomyces_avidinii Streptomyces avidinii] with <scene name='pdbligand=ACT:'>ACT</scene>, <scene name='pdbligand=SO4:'>SO4</scene> and <scene name='pdbligand=GLL:'>GLL</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2IZK OCA].
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*[[Avidin 3D structures|Avidin 3D structures]]
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__TOC__
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==Reference==
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</StructureSection>
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Binding of biotin to streptavidin stabilizes intersubunit salt bridges between Asp61 and His87 at low pH., Katz BA, J Mol Biol. 1997 Dec 19;274(5):776-800. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=9405158 9405158]
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[[Category: Large Structures]]
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[[Category: Single protein]]
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[[Category: Streptomyces avidinii]]
[[Category: Streptomyces avidinii]]
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[[Category: Katz, B A.]]
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[[Category: Katz BA]]
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[[Category: ACT]]
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[[Category: GLL]]
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[[Category: SO4]]
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[[Category: biotin-binding protein]]
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[[Category: designed small molecule ligand with micromolar affinity]]
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[[Category: streptavidin-small molecule ligand]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 17:57:45 2008''
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Current revision

STREPTAVIDIN-GLYCOLURIL PH 2.58 I4122 COMPLEX

PDB ID 2izk

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