Electrochemical and spectroscopic characterization of the 7Fe form of ferredoxin III from Desulfovibrio africanus.

Journal article

Desulfovibrio africanus ferredoxin III is a monomeric protein (Mr 6585) containing seven cysteine residues and 7-8 iron atoms and 6-8 atoms of acid-labile sulphur. It is shown that reversible unmediated electrochemistry of the two iron-sulphur clusters can be obtained by using a pyrolytic-graphite-'edge' carbon electrode in the presence of an appropriate aminoglycoside, neomycin or tobramycin, as promoter. Cyclic voltammetry reveals two well-defined reversible waves with E0' = -140 +/- 10 mV and -410 +/- 5 mV (standard hydrogen electrode) at 2 degrees C. Bulk reduction confirms that each of these corresponds to a one-electron process. Low-temperature e.p.r. and magnetic-c.d. spectroscopy identify the higher-potential redox couple with a cluster of core [3Fe-4S]1+.0 and the lower with a [4Fe-4S]2+.1+ centre. The low-temperature magnetic-c.d. spectra and magnetization properties of the three-iron cluster show that it is essentially identical with that in Desulfovibrio gigas ferredoxin II. We assign cysteine-11, -17 and -51 as ligands of the [3Fe-4S] core and cysteine-21, -41, -44 and -47 to the [4Fe-4S] centre.

Authors: Armstrong, F; George, S; Cammack, R; Hatchikian, E; Thomson, A

• Publication status: Published
• Journal: Biochemical journal
• Volume: 264
• Issue: 1
• Pages: 265-273
• Publication date: 1989-11-01
• EISSN: 1470-8728
• ISSN: 0264-6021
• Language: English
• Keywords: Electron Spin Resonance Spectroscopy; Neomycin; Tobramycin; Molecular Sequence Data; Iron; Hydrogen-Ion Concentration; Desulfovibrio; Circular Dichroism; Ferredoxins; Spectrum Analysis; Oxidation-Reduction; Magnetics; Amino Acid Sequence