Flavodoxin from the nitrogen-fixing cyanobacterium Anabaena PCC 7119 |
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Authors: | Maria F Fillat Gerhard Sandmann Carlos Gomez-Moreno |
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Institution: | (1) Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Spain;(2) Lehrstuhl für Physiologie und Biochemie der Pflanzen, Universität Konstanz, Germany |
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Abstract: | Flavodoxin has been isolated and purified from cultures of the cyanobacterium Anabaena cultivated in a low-iron medium. This flavoprotein has a molecular weight of 20,000 and contains 1 molecule of flavin mononucleotide per mol of protein. Various biochemical characteristics are reported including amino-acid composition, isoelectric point and the fluorescence properties of the apoprotein. The extinction coefficients and isosbestic points were determined for the oxidized and semiquinone forms of flavodoxin. The electron paramagnetic resonance spectrum of the semiquinone exhibited a spectral linewidth of 23 G, which is typical for a neutral flavoprotein semiquinone. Kinetic measurements give a rate constant of 9.6×107 (M-1 min-1) for the reduction of flavodoxin in the photosynthetic electron-transport chain by the photosystem I and 6.6×106 for the reaction in which flavodoxin is reduced by ferredoxin-NADP+ oxidoreductase. The Michaelis constant for electron donation to nitrogenase by reduced flavodoxin is 8.5 M.Abbreviations FMN
flavin mononucleotide
- FNR
ferredoxin-NADP+ oxidoreductase
- PSI
photosystem I |
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Keywords: | Anabaena Biochemical properties Flavodoxin Nitrogenase Photosystem-I electron transport Spectral characteristics |
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