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X-ray structure of E.coli Wrba in complex with FMN at 1.2 A resolution
Structural highlights
FunctionNQOR_ECOLI It seems to function in response to environmental stress when various electron transfer chains are affected or when the environment is highly oxidizing. It reduces quinones to the hydroquinone state to prevent interaction of the semiquinone with O2 and production of superoxide. It prefers NADH over NADPH.[1] [2] Publication Abstract from PubMedThe Escherichia coli protein WrbA, an FMN-dependent NAD(P)H:quinone oxidoreductase, was crystallized under new conditions in the presence of FAD or the native cofactor FMN. Slow-growing deep yellow crystals formed with FAD display the tetragonal bipyramidal shape typical for WrbA and diffract to 1.2 A resolution, the highest yet reported. Faster-growing deep yellow crystals formed with FMN display an atypical shape, but diffract to only approximately 1.6 A resolution and are not analysed further here. The 1.2 A resolution structure detailed here revealed only FMN in the active site and no electron density that can accommodate the missing parts of FAD. The very high resolution supports the modelling of the FMN isoalloxazine with a small but distinct propeller twist, apparently the first experimental observation of this predicted conformation, which appears to be enforced by the protein through a network of hydrogen bonds. Comparison of the electron density of the twisted isoalloxazine ring with the results of QM/MM simulations is compatible with the oxidized redox state. The very high resolution also supports the unique refinement of Met10 as the sulfoxide, confirmed by mass spectrometry. Bond lengths, intramolecular distances, and the pattern of hydrogen-bond donors and acceptors suggest the cofactor may interact with Met10. Slow incorporation of FMN, which is present as a trace contaminant in stocks of FAD, into growing crystals may be responsible for the near-atomic resolution, but a direct effect of the conformation of FMN and/or Met10 sulfoxide cannot be ruled out. 1.2 A resolution crystal structure of Escherichia coli WrbA holoprotein.,Kishko I, Carey J, Reha D, Brynda J, Winkler R, Harish B, Guerra R, Ettrichova O, Kukacka Z, Sheryemyetyeva O, Novak P, Kuty M, Kuta Smatanova I, Ettrich R, Lapkouski M Acta Crystallogr D Biol Crystallogr. 2013 Sep 1;69(Pt 9):1748-57. doi:, 10.1107/S0907444913017162. Epub 2013 Aug 15. PMID:23999298[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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