Differential activities of heterocyst ferredoxin,vegetative cell ferredoxin,and flavodoxin as electron carriers in nitrogen fixation and photosynthesis in Anabaena sp. |
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Authors: | P Razquin S Schmitz M L Peleato M F Fillat C Gómez-Moreno H Böhme |
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Institution: | (1) Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain;(2) Botanisches Insitut der Universitat Bonn, Kirschallee 1, 53115 Bonn, Germany |
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Abstract: | In cyanobacteria an increasing number of low potential electron carriers is found, but in most cases their contribution to metabolic pathways remains unclear. In this work, we compare recombinant plant-type ferredoxins from Anabaena sp. PCC 7120, encoded by the genes petF and fdxH, respectively, and flavodoxin from Anabaena sp. PCC 7119 as electron carriers in reconstituted in vitro assays with nitrogenase, Photosystem I, ferredoxin-NADP+ reductase and pyruvate-ferredoxin oxidoreductase. In every experimental system only the heterocyst ferredoxin catalyzed an efficient electron transfer to nitrogenase while vegetative cell ferredoxin and flavodoxin were much less active. This implies that flavodoxin is not able to functionally replace heterocyst ferredoxin. When PFO-activity in heterocyst extracts was reconstituted under anaerobic conditions, both ferredoxins were more efficient than flavodoxin, which suggested that this PFO was of the ferredoxin dependent type. Flavodoxin, synthesized under iron limiting conditions, replaces PetF very efficiently in the electron transport from Photosystem I to NADP+, using thylakoids from vegetative cells.Abbreviations BSA
bovine serum albumin
- FdxH
heterocyst ferredoxin
- Fld
flavodoxin
- FNR
ferredoxin-NADP+ reductase
- MV
methyl viologen
- PetF
vegetative cell ferredoxin
- PFO
pyruvate-ferredoxin oxidoreductase
- Pyr
piruvate
- PS I
Photosystem I |
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Keywords: | heterocyst ferredoxin vegetative cell ferredoxin flavodoxin nitrogen fixation NADP+ photoreduction pyruvate ferredoxin/flavodoxin oxidoreductase electron transport |
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