Clostridial characteristics

One of the characteristics of ferredoxin, as inferred from its name, is the presence of iron. Mortenson, Valentine, and Carnahan (75) reported non-heme iron in bacterial ferredoxin and several investigators independently reported non-heme iron in plant ferredoxin (Tagawa and Arnon (99) Fry and San Pietro (46) Horio and Yamashita (58)). Iron was also found in other clostridial ferredoxins (Lovenberg, Buchanan, and Rabinowitz (65)) and in ferredoxin of photosynthetic bacteria (Evans and Buchanan (41) Bachofen and Arnon (12)). Based on a molecular weight of 13,000, the plant ferredoxins which have been investigated contain 2 atoms of iron per molecule, but the iron content of bacterial ferredoxins differs. Clostridial ferredoxins contain 7 atoms of iron (Loven-... 

EPR spectra of the CO-reduced CODH complex from M. thermophila show features characteristic of the spin-coupled Ni-Fe-C center in C. thermoaceticum CODH (acetate synthase) [243,248]. Treatment of CO-reduced CODH complex of M. thermophila under N2 with acetyl-CoA perturbs these EPR features, an effect also observed with the clostridial enzyme [243,248], This perturbation is not observed with M. thermophila CODH complex if the gas phase is CO or if HS-CoA is used in place of acetyl-CoA [248] such is not the case with the C. thermoaceticum CODH [243],... 

Fe Protein. Characteristics of the Fe protein from Azotobacter 101) and Clostridia (94, 108) are summarized in Table VII. Clostridial Fe protein is stated to be 90-95% pure and the absence of tryptophan (102) suggests that almost all of the contaminating proteins have been removed. Recent preparations of Azotobacter Fe protein show specific activities even higher than those of clostridial Fe protein (101). The clostridial protein has a molecular weight of 39,000 and contains 2-3 Fe and 2 S atoms (94, 108). Molybdenum is absent, no ESR is detectable in the native protein (102) and, surprisingly, a resonance at g value of 1.94 has not been observed on reduction. All other purified iron-sulfur proteins with the exception of the atypical HIPIP and rubredoxin exhibit resonance in this area on reduction. One may suggest that the Fe protein is an atypical iron-sulfur protein or requires additional examination at 4°K for a resonance at g = 1.94. The individual protein has no activity alone but has all N2ase activities in combination with the Mo-Fe protein. 

One characteristic of clostridial butanol production is that it requires a high redox potential in order to produce butanol (and ethanol). That means, if a substrate is enriched with supplementary-reducing substances, this will intensify butanol and ethanol synthesis, but reduce acetone production (Mitchell 1998). 

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