Ferredoxins

Literature References: A group of electron transfer factors found in plants and bacteria, which are non-heme iron-sulfur proteins and which play an important role in photosynthesis, nitrogen and carbon dioxide fixation, and respiration. They are generally classified by the presence of either 2 or 4 iron atom clusters and an equivalent amount of inorganic or "acid-labile" sulfide bonded to the peptide chain through 4 cysteine sulfhydryl groups. The two-iron ferredoxins are found primarly in plants and blue-green algae and are sometimes referred to as chloroplast or "plant type" ferredoxins; the four-iron ferredoxins are predominant in bacteria. Mol wts of chloroplast ferredoxins are about 12,000; those of bacterial ferredoxins range from about 6,000 to 24,000. Isoln from Clostridium pasteurianum: L. E. Mortenson et al., Biochem. Biophys. Res. Commun. 7, 448 (1962). Prepn of bacterial ferredoxins: L. E. Mortenson, US 3344130 (1960 to duPont). The amino acid sequence of several bacterial and chloroplast ferredoxins has been elucidated. Amino acid sequence of ferredoxin from Clostridium pasteurianum: Tanaka et al., Biochem. Biophys. Res. Commun. 16, 422 (1964); eidem, Biochemistry 5, 1666 (1966); from spinach: Matsubara, Sasaki, J. Biol. Chem. 243, 1732 (1968). Synthesis of peptide chain of C. pasteurianum ferredoxins: Bayer et al., Tetrahedron 24, 4853 (1968); Trakatellis, Schwartz, Proc. Natl. Acad. Sci. USA 63, 436 (1969). Reviews: Buchanan, Struct. Bonding 1, 109 (1966); Malkin, Rabinowitz, Annu. Rev. Biochem. 36, 113 (1967); Arnon, Naturwissenschaften 56, 295 (1969); Buchanan, Arnon, Adv. Enzymol. 33, 119 (1970); W. Lovenberg, "Ferredoxin and Rubredoxin" in Microbial Iron Metabolism, J. B. Neilands, Ed. (Academic Press, New York, 1974) pp 161-182; D. C. Yoch, R. P. Carithers, Microbiol. Rev. 43, 384-421 (1979).

Properties: Absorption max of bacterial ferredoxins: 280, 385-400 nm; of plant ferredoxins: 280, 325, 420, 463 nm. All show negative oxidation-reduction potentials near that of the hydrogen electrode: -0.390 V (C. pasteurianum); -0.420 V (spinach): Tagawa, Arnon, Biochim. Biophys. Acta 153, 602 (1968). Autoxidizable. Acidification, as well as treatment with iron-chelating agents or mercurials, results in evolution of H2S and loss of the visible absorption.