View source for 4oqi


==Crystal structure of stabilized TEM-1 beta-lactamase variant v.13 carrying R164S/G238S mutations==
<StructureSection load='4oqi' size='340' side='right'caption='[[4oqi]], [[Resolution|resolution]] 1.13&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4oqi]] 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=4OQI OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4OQI 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]] 1.13&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</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=4oqi FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4oqi OCA], [https://pdbe.org/4oqi PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4oqi RCSB], [https://www.ebi.ac.uk/pdbsum/4oqi PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4oqi ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/Q8KMX3_ECOLX Q8KMX3_ECOLX] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Epistasis is a key factor in evolution since it determines which combinations of mutations provide adaptive solutions and which mutational pathways toward these solutions are accessible by natural selection. There is growing evidence for the pervasiveness of sign epistasis--a complete reversion of mutational effects, particularly in protein evolution--yet its molecular basis remains poorly understood. We describe the structural basis of sign epistasis between G238S and R164S, two adaptive mutations in TEM-1 beta-lactamase--an enzyme that endows antibiotics resistance. Separated by 10 A, these mutations initiate two separate trajectories toward increased hydrolysis rates and resistance toward second and third-generation cephalosporins antibiotics. Both mutations allow the enzyme's active site to adopt alternative conformations and accommodate the new antibiotics. By solving the corresponding set of crystal structures, we found that R164S causes local disorder whereas G238S induces discrete conformations. When combined, the mutations in 238 and 164 induce local disorder whereby nonproductive conformations that perturb the enzyme's catalytic preorganization dominate. Specifically, Asn170 that coordinates the deacylating water molecule is misaligned, in both the free form and the inhibitor-bound double mutant. This local disorder is not restored by stabilizing global suppressor mutations and thus leads to an evolutionary cul-de-sac. Conformational dynamism therefore underlines the reshaping potential of protein's structures and functions but also limits protein evolvability because of the fragility of the interactions networks that maintain protein structures.

Negative Epistasis and Evolvability in TEM-1 beta-Lactamase--The Thin Line between an Enzyme's Conformational Freedom and Disorder.,Dellus-Gur E, Elias M, Caselli E, Prati F, Salverda ML, de Visser JA, Fraser JS, Tawfik DS J Mol Biol. 2015 Jul 17;427(14):2396-409. doi: 10.1016/j.jmb.2015.05.011. Epub, 2015 May 22. PMID:26004540<ref>PMID:26004540</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4oqi" style="background-color:#fffaf0;"></div>

==See Also==
*[[Beta-lactamase 3D structures|Beta-lactamase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Escherichia coli]]
[[Category: Large Structures]]
[[Category: Dellus-Gur E]]
[[Category: Elias M]]
[[Category: Fraser JS]]
[[Category: Tawfik DS]]