4pu0

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=FMN:FLAVIN+MONONUCLEOTIDE'>FMN</scene>, <scene name='pdbligand=GOL:GLYCEROL'>GOL</scene>, <scene name='pdbligand=PO4:PHOSPHATE+ION'>PO4</scene></td></tr>

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== Publication Abstract from PubMed ==

The Escherichia coli sulfur starvation utilization (ssu) operon includes a two-component monooxygenase system consisting of a nicotinamide adenine dinucleotide phosphate (NADPH)-dependent flavin mononucleotide (FMN) reductase, SsuE, and a monooxygenase, SsuD. SsuE is part of the flavodoxin-like superfamily, and we report here the crystal structures of its apo, FMN-bound, and FMNH2-bound forms at approximately 2 A resolution. In the crystals, SsuE forms a tetramer that is a dimer of dimers similar to those seen for homologous FMN reductases, quinone reductases, and the WrbA family of enzymes. A pi-helix present at the tetramer building interface is unique to the reductases from two-component monooxygenase systems. Analytical ultracentrifugation studies of SsuE confirm a dimer-tetramer equilibrium exists in solution, with FMN binding favoring the dimer. As the active site includes residues from both subunits, at least a dimeric association is required for the function of SsuE. The structures show that one FMN binds tightly in a deeply held site, which makes available a second binding site, in which either a second FMN or the nicotinamide of NADPH can bind. The FMNH2-bound structure shows subtle changes consistent with its binding being weaker than that of FMN. Combining this information with published kinetic studies, we propose a general catalytic cycle for two-component reductases of the flavodoxin-like superfamily, by which the enzyme can potentially provide FMNH2 to its partner monooxygenase by different routes depending on the FMN concentration and the presence of a partner monooxygenase.

Crystal Structure of Escherichia coli SsuE: Defining a General Catalytic Cycle for FMN Reductases of the Flavodoxin-like Superfamily.,Driggers CM, Dayal PV, Ellis HR, Karplus PA Biochemistry. 2014 Jun 3;53(21):3509-19. doi: 10.1021/bi500314f. Epub 2014 May, 21. PMID:24816272<ref>PMID:24816272</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

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