View source for 1kl4


==AN ENGINEERED STREPTAVIDIN WITH IMPROVED AFFINITY FOR THE STREP-TAG II PEPTIDE : apo-SAM2==
<StructureSection load='1kl4' size='340' side='right'caption='[[1kl4]], [[Resolution|resolution]] 1.70&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1kl4]] 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=1KL4 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1KL4 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]] 1.7&#8491;</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=1kl4 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1kl4 OCA], [https://pdbe.org/1kl4 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1kl4 RCSB], [https://www.ebi.ac.uk/pdbsum/1kl4 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1kl4 ProSAT]</span></td></tr>
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== Function ==
[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).
== 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/kl/1kl4_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=1kl4 ConSurf].
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== Publication Abstract from PubMed ==
The Strep-tag II is a nine-amino acid peptide that was developed as an affinity tool for the purification of corresponding fusion proteins on streptavidin columns. The peptide recognizes the same pocket of streptavidin where the natural ligand is normally bound so that biotin or its chemical derivatives can be used for competitive elution. We report here the crystal structures of the streptavidin mutants '1' and '2,' which had been engineered for 10-fold higher affinity towards the Strep-tag II. Both streptavidin mutants carry mutations at positions 44, 45, and 47, that is, in a flexible loop region close to the binding site. The crystal structures of the two apo-proteins and their complexes with the Strep-tag II peptide were refined at resolutions below 2 A. Both in the presence and absence of the peptide, the lid-like loop next to the ligand pocket--comprising residues 45 through 52--adopts an 'open' conformation in all four subunits within the asymmetric unit. The same loop was previously described to be disordered in the wild-type apo-streptavidin and to close over the pocket upon complexation of the natural ligand biotin. Our findings suggest that stabilization of the 'open' loop conformation in the absence of a ligand abolishes the need for conformational rearrangement prior to the docking of the voluminous peptide. Because no direct contacts between the flexible part of the loop and the peptide ligand were detected, it seems likely that the higher affinity of the two streptavidin mutants for the Strep-tag II is caused by a predominantly entropic mechanism.

Improved affinity of engineered streptavidin for the Strep-tag II peptide is due to a fixed open conformation of the lid-like loop at the binding site.,Korndorfer IP, Skerra A Protein Sci. 2002 Apr;11(4):883-93. PMID:11910031<ref>PMID:11910031</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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==See Also==
*[[Avidin 3D structures|Avidin 3D structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Large Structures]]
[[Category: Streptomyces avidinii]]
[[Category: Korndoerfer IP]]
[[Category: Skerra A]]