1swa

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(New page: 200px<br /><applet load="1swa" size="450" color="white" frame="true" align="right" spinBox="true" caption="1swa, resolution 1.9&Aring;" /> '''APO-CORE-STREPTAVIDIN...)
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[[Image:1swa.gif|left|200px]]<br /><applet load="1swa" size="450" color="white" frame="true" align="right" spinBox="true"
 
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caption="1swa, resolution 1.9&Aring;" />
 
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'''APO-CORE-STREPTAVIDIN AT PH 4.5'''<br />
 
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==Overview==
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==APO-CORE-STREPTAVIDIN AT PH 4.5==
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The streptavidin-biotin complex provides the basis for many important, biotechnological applications and is an interesting model system for, studying high-affinity protein-ligand interactions. We report here, crystallographic studies elucidating the conformation of the flexible, binding loop of streptavidin (residues 45 to 52) in the unbound and bound, forms. The crystal structures of unbound streptavidin have been determined, in two monoclinic crystal forms. The binding loop generally adopts an open, conformation in the unbound species. In one subunit of one crystal form, the flexible loop adopts the closed conformation and an analysis of, packing interactions suggests that protein-protein contacts stabilize the, closed loop conformation. In the other crystal form all loops adopt an, open conformation. Co-crystallization of streptavidin and biotin resulted, in two additional, different crystal forms, with ligand bound in all four, binding sites of the first crystal form and biotin bound in only two, subunits in a second. The major change associated with binding of biotin, is the closure of the surface loop incorporating residues 45 to 52., Residues 49 to 52 display a 3(10) helical conformation in unbound subunits, of our structures as opposed to the disordered loops observed in other, structure determinations of streptavidin. In addition, the open, conformation is stabilized by a beta-sheet hydrogen bond between residues, 45 and 52, which cannot occur in the closed conformation. The 3(10) helix, is observed in nearly all unbound subunits of both the co-crystallized and, ligand-free structures. An analysis of the temperature factors of the, binding loop regions suggests that the mobility of the closed loops in the, complexed structures is lower than in the open loops of the ligand-free, structures. The two biotin bound subunits in the tetramer found in the, MONO-b1 crystal form are those that contribute Trp 120 across their, respective binding pockets, suggesting a structural link between these, binding sites in the tetramer. However, there are no obvious signatures of, binding site communication observed upon ligand binding, such as, quaternary structure changes or shifts in the region of Trp 120. These, studies demonstrate that while crystallographic packing interactions can, stabilize both the open and closed forms of the flexible loop, in their, absence the loop is open in the unbound state and closed in the presence, of biotin. If present in solution, the helical structure in the open loop, conformation could moderate the entropic penalty associated with biotin, binding by contributing an order-to-disorder component to the loop, closure.
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<StructureSection load='1swa' size='340' side='right'caption='[[1swa]], [[Resolution|resolution]] 1.90&Aring;' scene=''>
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== Structural highlights ==
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<table><tr><td colspan='2'>[[1swa]] is a 4 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=1SWA OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1SWA 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]] 1.9&#8491;</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=1swa FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1swa OCA], [https://pdbe.org/1swa PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1swa RCSB], [https://www.ebi.ac.uk/pdbsum/1swa PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1swa 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/sw/1swa_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=1swa 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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1SWA is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Streptomyces_avidinii Streptomyces avidinii]. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1SWA 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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Structural studies of the streptavidin binding loop., Freitag S, Le Trong I, Klumb L, Stayton PS, Stenkamp RE, Protein Sci. 1997 Jun;6(6):1157-66. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=9194176 9194176]
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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: Freitag, S.]]
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[[Category: Freitag S]]
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[[Category: Klumb, L.]]
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[[Category: Klumb L]]
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[[Category: Stayton, P.S.]]
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[[Category: Le Trong I]]
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[[Category: Stenkamp, R.E.]]
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[[Category: Stayton PS]]
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[[Category: Trong, I.Le.]]
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[[Category: Stenkamp RE]]
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[[Category: biotin]]
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[[Category: biotin-binding protein]]
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[[Category: signal]]
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''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Wed Nov 21 02:46:49 2007''
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APO-CORE-STREPTAVIDIN AT PH 4.5

PDB ID 1swa

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