title: A new plant-type ferredoxin from halobacteria.
abstract: A stable, 2Fe-type ferredoxin has been prepared from Halobacterium halobium and purified by chromatography. A similar ferredoxin was also found in three other Halobacteria. The ferredoxin is present in large amounts-about 1 percent of the total soluble protein. From amino acid composition a molecular weight of 14800 +/- 200 was calculated. The ferredoxin was found to contain two atoms each of iron and sulphide. The midpoint redox potential of the protein is about -345 mV. The electron paramagnetic resonance spectrum of the reduced form shows much similarity to plant and algal ferredoxins with gx = 1.90, gy = 1.97 and gz = 2.07. The same similarity is observed in the optical absorption, optical rotatory dispersion and circular dichroism spectra. However it does not seem to mediate electron transport in the NADP-photoreduction system of chloroplasts. Extracts of the bacterial cells catalyze the reduction of the ferredoxin by NADH.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D005288:Ferredoxins / Q000032:analysis; D006217:Halobacterium / Q000032:analysis*; D007501:Iron / Q000032:analysis; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000032:analysis; D011487:Protein Conformation; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013455:Sulfur / Q000032:analysis
chemical_list: D000596:Amino Acids; D005288:Ferredoxins; D010940:Plant Proteins; D013455:Sulfur; D007501:Iron