title: Characterization of two 2[4Fe4S] ferredoxins from Clostridium acetobutylicum.
abstract: In vivo hydrogen production in Clostridium acetobutylicum involves electron transfer between ferredoxin and [FeFe]-hydrogenase. Five C. acetobutylicum open reading frames were annotated as coding for putative ferredoxins. We focused our biophysical and biochemical investigations on CAC0303 and CAC3527, which possess the sequence signature and length of classical 2[4Fe4S] clostridial ferredoxins but differ significantly in theoretical pI. After cloning, heterologous expression in E. coli followed by in vitro Fe-S incorporation and purification, CAC0303 was shown to have a regular electron paramagnetic resonance (EPR) signal for a classical 2[4Fe4S] clostridial ferredoxin, while CAC3527 displayed an unusual EPR signal and a quite low reduction potential. Both ferredoxins were reduced in vitro by C. acetobutylicum [FeFe]-hydrogenase, but the CAC3527 reduction rate was 10-fold lower than that of CAC0303. These results are consistent with the efficiency of intermolecular electron transfer being dictated by the redox thermodynamics, the contribution of the ferredoxin global charge being only minor. The physiological function of CAC3527 is discussed.
authors: UMR5504, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, CNRS, INRA, INSA, Toulouse F-31400, France.
authors: Olivier
authors: O
authors: Guerrini
authors: Bénédicte
authors: B
authors: Burlat
authors: Christophe
authors: C
authors: Léger
authors: Bruno
authors: B
authors: Guigliarelli
authors: Philippe
authors: P
authors: Soucaille
authors: Laurence
authors: L
authors: Girbal
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D046969:Clostridium acetobutylicum / Q000235:genetics / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005288:Ferredoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006864:Hydrogenase / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D017422:Sequence Analysis, DNA
chemical_list: D005288:Ferredoxins; D007506:Iron-Sulfur Proteins; D006864:Hydrogenase