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==E. coli Quinol fumarate reductase FrdA E245Q mutation==
<StructureSection load='5vpn' size='340' side='right'caption='[[5vpn]], [[Resolution|resolution]] 4.22&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5vpn]] is a 8 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] and [https://en.wikipedia.org/wiki/Escherichia_coli_K-12 Escherichia coli K-12]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5VPN OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=5VPN 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]] 4.2232&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=FAD:FLAVIN-ADENINE+DINUCLEOTIDE'>FAD</scene>, <scene name='pdbligand=FES:FE2/S2+(INORGANIC)+CLUSTER'>FES</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=5vpn FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5vpn OCA], [https://pdbe.org/5vpn PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=5vpn RCSB], [https://www.ebi.ac.uk/pdbsum/5vpn PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=5vpn ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/FRDA_ECOLI FRDA_ECOLI] Two distinct, membrane-bound, FAD-containing enzymes are responsible for the catalysis of fumarate and succinate interconversion; the fumarate reductase is used in anaerobic growth, and the succinate dehydrogenase is used in aerobic growth.
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The Escherichia coli Complex II homolog quinol:fumarate reductase (QFR, FrdABCD) catalyzes the interconversion of fumarate and succinate at a covalently attached FAD within the FrdA subunit. The SdhE assembly factor enhances covalent flavinylation of Complex II homologs, but the mechanisms underlying the covalent attachment of FAD remain to be fully elucidated. Here, we explored the mechanisms of covalent flavinylation of the E. coli QFR FrdA subunit. Using a DeltasdhE E. coli strain, we show that the requirement for the assembly factor depends on the cellular redox environment. We next identified residues important for the covalent attachment and selected the FrdAE245 residue, which contributes to proton shuttling during fumarate reduction, for detailed biophysical and structural characterization. We found that QFR complexes containing FrdAE245Q have a structure similar to that of the WT flavoprotein, but lack detectable substrate binding and turnover. In the context of the isolated FrdA subunit, the anticipated assembly intermediate during covalent flavinylation, FrdAE245 variants had stability similar to that of WT FrdA, contained noncovalent FAD, and displayed a reduced capacity to interact with SdhE. However, small-angle X-ray scattering (SAXS) analysis of WT FrdA crosslinked to SdhE suggested that the FrdAE245 residue is unlikely to contribute directly to the FrdA-SdhE protein-protein interface. We also found that no auxiliary factor is absolutely required for flavinylation, indicating that the covalent flavinylation is autocatalytic. We propose that multiple factors, including the SdhE assembly factor and bound dicarboxylates, stimulate covalent flavinylation by preorganizing the active site to stabilize the quinone-methide intermediate.

Structural and biochemical analyses reveal insights into covalent flavinylation of the Escherichia coli Complex II homolog quinol:fumarate reductase.,Starbird CA, Maklashina E, Sharma P, Qualls-Histed S, Cecchini G, Iverson TM J Biol Chem. 2017 Jun 14. pii: jbc.M117.795120. doi: 10.1074/jbc.M117.795120. PMID:28615448<ref>PMID:28615448</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 5vpn" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Escherichia coli]]
[[Category: Escherichia coli K-12]]
[[Category: Large Structures]]
[[Category: Cecchini G]]
[[Category: Iverson TM]]
[[Category: Maklashina E]]
[[Category: Qualls-Histed S]]
[[Category: Sharma P]]
[[Category: Starbird CA]]