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| [[Image:2b57.gif|left|200px]]<br /><applet load="2b57" size="350" color="white" frame="true" align="right" spinBox="true"
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| caption="2b57, resolution 2.15Å" />
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| '''Guanine Riboswitch C74U mutant bound to 2,6-diaminopurine'''<br />
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| ==Overview== | | ==Guanine Riboswitch C74U mutant bound to 2,6-diaminopurine== |
| Riboswitches are cis-acting genetic regulatory elements found commonly in bacterial mRNAs that consist of a metabolite-responsive aptamer domain coupled to a regulatory switch. Purine riboswitches respond to intracellular concentrations of either adenine or guanine/hypoxanthine to control gene expression. The aptamer domain of the purine riboswitch contains a pyrimidine residue (Y74) that forms a Watson-Crick base-pairing interaction with the bound purine nucleobase ligand that discriminates between adenine and guanine. We sought to understand the structural basis of this specificity and the mechanism of ligand recognition by the purine riboswitch. Here, we present the 2,6-diaminopurine-bound structure of a C74U mutant of the xpt-pbuX guanine riboswitch, along with a detailed thermodynamic and kinetic analysis of nucleobase recognition by both the native and mutant riboswitches. These studies demonstrate clearly that the pyrimidine at position 74 is the sole determinant of purine riboswitch specificity. In addition, the mutant riboswitch binds adenine and adenine derivatives well compared with the guanine-responsive riboswitch. Under our experimental conditions, 2,6-diaminopurine binds the RNA with DeltaH=-40.3 kcal mol(-1), DeltaS=-97.6 cal mol(-1)K(-1), and DeltaG=-10.73 kcal mol(-1). A kinetic determination of the slow rate (0.15 x 10(5)M(-1)s(-1) and 2.1 x 10(5)mM(-1)s(-1) for 2-aminopurine binding the adenine-responsive mutant riboswitch and 7-deazaguanine-binding guanine riboswitch, respectively) of association under varying experimental conditions allowed us to propose a mechanism for ligand recognition by the purine riboswitch. A conformationally dynamic unliganded state for the binding pocket is stabilized first by the Watson-Crick base pairing between the ligand and Y74, and by the subsequent ordering of the J2/3 loop, enclosing the ligand within the three-way junction.
| | <StructureSection load='2b57' size='340' side='right'caption='[[2b57]], [[Resolution|resolution]] 2.15Å' scene=''> |
| | == Structural highlights == |
| | <table><tr><td colspan='2'>[[2b57]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Bacillus_subtilis Bacillus subtilis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2B57 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2B57 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]] 2.15Å</td></tr> |
| | <tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=6AP:9H-PURINE-2,6-DIAMINE'>6AP</scene>, <scene name='pdbligand=ACT:ACETATE+ION'>ACT</scene>, <scene name='pdbligand=NCO:COBALT+HEXAMMINE(III)'>NCO</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=2b57 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2b57 OCA], [https://pdbe.org/2b57 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2b57 RCSB], [https://www.ebi.ac.uk/pdbsum/2b57 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2b57 ProSAT]</span></td></tr> |
| | </table> |
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| ==About this Structure== | | ==See Also== |
| 2B57 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/ ] with <scene name='pdbligand=ACT:'>ACT</scene>, <scene name='pdbligand=NCO:'>NCO</scene> and <scene name='pdbligand=6AP:'>6AP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2B57 OCA].
| | *[[Riboswitch 3D structures|Riboswitch 3D structures]] |
| | | __TOC__ |
| ==Reference==
| | </StructureSection> |
| Thermodynamic and kinetic characterization of ligand binding to the purine riboswitch aptamer domain., Gilbert SD, Stoddard CD, Wise SJ, Batey RT, J Mol Biol. 2006 Jun 9;359(3):754-68. Epub 2006 Apr 21. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=16650860 16650860]
| | [[Category: Bacillus subtilis]] |
| [[Category: Single protein]] | | [[Category: Large Structures]] |
| [[Category: Batey, R T.]] | | [[Category: Batey RT]] |
| [[Category: Gilbert, S D.]] | | [[Category: Gilbert SD]] |
| [[Category: Stoddard, C D.]] | | [[Category: Stoddard CD]] |
| [[Category: Wise, S J.]] | | [[Category: Wise SJ]] |
| [[Category: 6AP]]
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| [[Category: ACT]]
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| [[Category: NCO]]
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| [[Category: base quadruples]]
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| [[Category: base triples]]
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| [[Category: double helix]]
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| [[Category: mrna]]
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| [[Category: purine]]
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| [[Category: rna-ligand complex]]
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| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:34:17 2008''
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