View source for 4qlg


==Crystal structure of I14V DHFR mutant complexed with folate and NADP+==
<StructureSection load='4qlg' size='340' side='right'caption='[[4qlg]], [[Resolution|resolution]] 1.50&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4qlg]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli_str._K-12_substr._MC4100 Escherichia coli str. K-12 substr. MC4100]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4QLG OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4QLG 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]] 1.5&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=FOL:FOLIC+ACID'>FOL</scene>, <scene name='pdbligand=NAP:NADP+NICOTINAMIDE-ADENINE-DINUCLEOTIDE+PHOSPHATE'>NAP</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=4qlg FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4qlg OCA], [https://pdbe.org/4qlg PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4qlg RCSB], [https://www.ebi.ac.uk/pdbsum/4qlg PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4qlg ProSAT]</span></td></tr>
</table>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
This study employs hybrid quantum mechanics-molecular mechanics (QM/MM) simulations to investigate the effect of mutations of the active-site residue I14 of E. coli dihydrofolate reductase (DHFR) on the hydride transfer. Recent kinetic measurements of the I14X mutants (X = V, A, and G) indicated slower hydride transfer rates and increasingly temperature-dependent kinetic isotope effects (KIEs) with systematic reduction of the I14 side chain. The QM/MM simulations show that when the original isoleucine residue is substituted in silico by valine, alanine, or glycine (I14V, I14A, and I14G DHFR, respectively), the free energy barrier height of the hydride transfer reaction increases relative to the wild-type enzyme. These trends are in line with the single-turnover rate measurements reported for these systems. In addition, extended dynamics simulations of the reactive Michaelis complex reveal enhanced flexibility in the mutants, and in particular for the I14G mutant, including considerable fluctuations of the donor-acceptor distance (DAD) and the active-site hydrogen bonding network compared with those detected in the native enzyme. These observations suggest that the perturbations induced by the mutations partly impair the active-site environment in the reactant state. On the other hand, the average DADs at the transition state of all DHFR variants are similar. Crystal structures of I14 mutants (V, A, and G) confirmed the trend of increased flexibility of the M20 and other loops.

Free Energy Simulations of Active-Site Mutants of Dihydrofolate Reductase.,Doron D, Stojkovic V, Gakhar L, Vardi-Kilshtain A, Kohen A, Major DT J Phys Chem B. 2014 Nov 21. PMID:25382260<ref>PMID:25382260</ref>

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

==See Also==
*[[Dihydrofolate reductase 3D structures|Dihydrofolate reductase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Escherichia coli str. K-12 substr. MC4100]]
[[Category: Large Structures]]
[[Category: Gakhar L]]
[[Category: Kohen A]]
[[Category: Stojkovic V]]