The formation of the iron-sulfur cluster of ferredoxin was examined in vitro by incubating isolated chloroplasts with [(35)S]cysteine. The ferredoxin molecule was radioactively labeled in chloroplasts without synthesis of its polypeptide and comigrated with holoferredoxin during polyacrylamide gel electrophoresis under nondenaturing conditions. When the labeled ferredoxin was denatured by the a...

Ferredoxin is a typical iron-sulfur protein that is ubiquitous in biological redox systems. This study investigates the in vitro assembly of a [Fe2S2] cluster in the ferredoxin from Acidithiobacillus ferrooxidans in the presence of three scaffold proteins: IscA, IscS, and IscU. The spectra and MALDI-TOF MS results for the reconstituted ferredoxin confirm that the iron-sulfur cluster was correct...

Clostridium pasteurianum cell-free extracts enzymatically reduced metronidazole when coupled by hydrogenase via reduced ferredoxin. A 5 mM concentration of methyl viologen, flavin adenine dinucleotide, or flavin mononucleotide could completely replace ferredoxin (0.05 mM) in the in vitro reduction assay system, whereas 5 mM benzyl viologen was less effective. However, when these electron carrie...

Friedreich's ataxia is caused by a deficit in frataxin, a small mitochondrial protein of unknown function that has been conserved during evolution. Previous studies have pointed out a role for frataxin in mitochondrial iron-sulfur (Fe-S) metabolism. Here, we have analyzed the incorporation of Fe-S clusters into yeast ferredoxin imported into isolated energized mitochondria from cells grown in t...

A growing number of processes throughout biology are regulated by redox via thiol-disulfide exchange. This mechanism is particularly widespread in plants, where almost 200 proteins have been linked to thioredoxin (Trx), a widely distributed small regulatory disulfide protein. The current study extends regulation by Trx to amyloplasts, organelles prevalent in heterotrophic plant tissues that, am...

It has been shown by difference spectroscopy that purified ferredoxin and ferredoxin-NADP reductase form a complex. The absorption maxima due to the interaction of the proteins are at 395, 469, and 495 nm. Bleached ferredoxin does not form such a complex. The stoichiometry of the complex is 2 molecules of ferredoxin per 1 molecule of flavoprotein. The complex is decomposed by salts but not by u...

The mechanism of regulation of NADPH-ferredoxin reductase was studied in cell-free lysates of Clostridium kluyveri. The following activities, which are assumed to be linked to the enzyme, were investigated: ferredoxin reduction by NADPH, NADPf reduction by reduced ferredoxin, transhydrogenation from NADPH to NAD+, and methyl viologen reduction by NADPH. Ferredoxin reduction by NADPH is controll...

The electronic absorption spectra of oxidized and reduced spinach ferredoxins have been measured between 1200 and 600 nm at low temperature in D(2)O/ethylene glycol glasses. Relatively weak absorption bands are observed at 720, 820, and 920 nm in oxidized ferredoxin, and at 652, 820, and 920 nm in reduced ferredoxin. The spectral results show that the two Fe(III) centers in oxidized ferredoxin ...

Photosystem I is a highly efficient and potent light-induced reductase that is considered to be an appealing target for integration into hybrid solar fuel production systems. However, rapid transport of multiple electrons from the reducing end of photosystem I to downstream processes in vivo is limited by the diffusion of its native redox partner ferredoxin that is a single electron carrier. He...