View source for 4p68


==Electrostatics of Active Site Microenvironments for E. coli DHFR==
<StructureSection load='4p68' size='340' side='right'caption='[[4p68]], [[Resolution|resolution]] 2.26&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4p68]] 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=4P68 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4P68 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]] 2.26&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ACT:ACETATE+ION'>ACT</scene>, <scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=MTX:METHOTREXATE'>MTX</scene>, <scene name='pdbligand=NAP:NADP+NICOTINAMIDE-ADENINE-DINUCLEOTIDE+PHOSPHATE'>NAP</scene>, <scene name='pdbligand=XCN:S-CYANO-L-CYSTEINE'>XCN</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=4p68 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4p68 OCA], [https://pdbe.org/4p68 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4p68 RCSB], [https://www.ebi.ac.uk/pdbsum/4p68 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4p68 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/C3TR70_ECOLX C3TR70_ECOLX] Key enzyme in folate metabolism. Catalyzes an essential reaction for de novo glycine and purine synthesis, and for DNA precursor synthesis (By similarity).[PIRNR:PIRNR000194]
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== Publication Abstract from PubMed ==
Electrostatic interactions play an important role in enzyme catalysis by guiding ligand binding and facilitating chemical reactions. These electrostatic interactions are modulated by conformational changes occurring over the catalytic cycle. Herein, the changes in active site electrostatic microenvironments are examined for all enzyme complexes along the catalytic cycle of Escherichia coli dihydrofolate reductase (ecDHFR) by incorporation of thiocyanate probes at two site-specific locations in the active site. The electrostatics and degree of hydration of the microenvironments surrounding the probes are investigated with spectroscopic techniques and mixed quantum mechanical/molecular mechanical (QM/MM) calculations. Changes in the electrostatic microenvironments along the catalytic environment lead to different nitrile (CN) vibrational stretching frequencies and 13C NMR chemical shifts. These environmental changes arise from protein conformational rearrangements during catalysis. The QM/MM calculations reproduce the experimentally measured vibrational frequency shifts of the thiocyanate probes across the catalyzed hydride transfer step, which spans the closed and occluded conformations of the enzyme. Analysis of the molecular dynamics trajectories provides insight into the conformational changes occurring between these two states and the resulting changes in classical electrostatics and specific hydrogen-bonding interactions. The electric fields along the CN axes of the probes are decomposed into contributions from specific residues, ligands, and solvent molecules that make up the microenvironments around the probes. Moreover, calculation of the electric field along the hydride donor-acceptor axis, along with decomposition of this field into specific contributions, indicates that the cofactor and substrate, as well as the enzyme, impose a substantial electric field that facilitates hydride transfer. Overall, experimental and theoretical data provide evidence for significant electrostatic changes in the active site microenvironments due to conformational motion occurring over the catalytic cycle of ecDHFR.

Probing the Electrostatics of Active Site Microenvironments along the Catalytic Cycle for Escherichia coli Dihydrofolate Reductase.,Liu CT, Layfield JP, Stewart RJ 3rd, French JB, Hanoian P, Asbury JB, Hammes-Schiffer S, Benkovic SJ J Am Chem Soc. 2014 Jul 11. PMID:24977791<ref>PMID:24977791</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 4p68" style="background-color:#fffaf0;"></div>

==See Also==
*[[Dihydrofolate reductase 3D structures|Dihydrofolate reductase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Escherichia coli]]
[[Category: Large Structures]]
[[Category: Asbury JB]]
[[Category: Benkovic SJ]]
[[Category: French JB]]
[[Category: Hammes-Schiffer S]]
[[Category: Hanoian P]]
[[Category: Layfield JP]]
[[Category: Liu CT]]
[[Category: Stewart III RJ]]