Crystallisation of the flavodoxin from Megasphaera eldenii .
نویسندگان
چکیده
Flavodoxins are small flavoproteins (M, 15000-22000), that have been found in several strains of bacteria and algae [ I ] The protein contains one molecule of non-covalently bound FMN and hnctions biochemically as a one-electron carrier between the semiquinone and hlly reduced forms. Under iron-deficient conditions the protein is produced by Megasphaera elsdenii to replace the iron-sulphur protein ferredoxin [ I ] , Megasphaera elsdenii is a rumen bacterium that ferments lactate to molecular hydrogen, COZ and short-chain fatty acids which are excreted into the growth medium [2] Flavodoxin in this organism transfers electron produced in the oxidation of pyruvate to other redox proteins. The Fh4N when bound to the apoprotein has strongly altered redox potentials as compared to free FMN [ I ] . Redox potential regulation of the flavin by the protein is central to understanding the mechanisms of flavoprotein-catalyzed reactions. Experiments to investigate the interaction between FMN and apoprotein have involved kinetic, redox and thermodynamic calculations, often using modified flavins, NMR studies and x-ray crystallography. M. elsdenir flavodoxin because it is easily purified in large quantities and is remarkably stable in the three redox states has been extensively studied more than most flavoproteins. However until this time no three dimensional crystallographic structure has been available Crystal structures have been determined for three flavodoxins [3,4) Surprisingly although there is much sequence homology the detailed structure around the flavin at the active centre varies between Crystals were reduced with excess dithionite and sealed in x-ray capillaries in an anaerobic environment. The orthorhombic shaped crystals were yellow when oxidised and redpurple in the semireduced state. Crystals survived well during data collection using synchrotron radiation.
منابع مشابه
Efficiency of ferredoxins and flavodoxins as mediators in systems for hydrogen evolution.
1. The efficiencies of ferredoxins and flavodoxins from a range of sources as mediators in systems for hydrogen evolution were assessed. 2. In supporting electron transfer from dithionite to hydrogenase of the bacterium Clostridium pasteurianum, highest activity was shown by the ferredoxin from the cyanobacterium Chlorogloeopsis fritschii and flavodoxin from the bacterium Megasphaera elsdenii. ...
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1 The reactions of the oxidised and semiquinone forms of Peptostreptococcus elsdenii flavodoxin with sodium dithionite have been studied by stopped flow spectrophotometry. At low ionic strength where comproportionation of flavodoxin is slow compared with the overall rate of reduction, the reactions with an excess of dithionite follow first-order kinetics. Semiquinone is not detected during the ...
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The broadening of protein nuclear magnetic resonances in the spectra of the semiquinone forms of flavodoxins derived from Clostridium MP and Peptostreptococcus elsdenii relative to the resonances in the oxidized and reduced forms is highly selective. Spectra from both species of flavodoxin indicate that conformational differences between the oxidized and fully reduced states are minor and, cons...
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The time-resolved fluorescence and fluorescence anisotropy characteristics of reduced flavin mononucleotide in solution as well as bound in flavodoxins isolated from the bacteria Desulfovibrio gigas, DesuIfovibrio vulgaris, Clostridium beijerinckii MP and Megasphaera elsdenii have been examined. All fluorescence and fluorescence anisotropy decays were analyzed by two different methods : (a) lea...
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عنوان ژورنال:
- Biochemical Society transactions
دوره 24 1 شماره
صفحات -
تاریخ انتشار 1996