Reduction of the ferrous alpha-verdoheme-cytochrome b5 complex.
The ferrous alpha-verdoheme-cytochrome b(5) complex, [Fe(II)(verdoheme)](+), has been prepared and characterized spectroscopically. Anaerobic addition of excess sodium dithionite to [Fe(II)(verdoheme)](+) at pH 10 produces a one-electron-reduced species with spectroscopic characteristics that suggest a ferrous hexacoordinated verdoheme pineutral radical best formulated as a [Fe(II)(verdoheme*)] --> [Fe(I)(verdoheme)] resonance hybrid. At lower pH values (7.0 and 8.0) the one-electron-reduced species is shown to disproportionate to produce the resting state [Fe(II)(verdoheme)](+) complex and the two-electron-reduced [Fe(II)(verdoheme:)](-) anion. The latter might also be formulated as a resonance hybrid [Fe(I)(verdoheme*)](-) --> [Fe(II)(verdoheme:)](-). The disproportionation reaction becomes very slow as the pH is raised above 9.0. Exposure of the one-electron- or two-electron-reduced verdoheme complexes of cytochrome b(5) to O(2) results in rapid and quantitative reoxidation to the resting state [Fe(II)(verdoheme)](+) complex.
Damaso
Christopher O
CO
Department of Chemistry, University of Kansas, Lawrence, Kansas 66045-7582, USA.
Rubie
Nick D
ND
Moënne-Loccoz
Pierre
P
Rivera
Mario
M
D000818:Animals; D015786:Cytochromes b5 / Q000737:chemistry* / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D005296:Ferrous Compounds / Q000737:chemistry* / Q000378:metabolism; D006418:Heme / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology*; D008928:Mitochondria / Q000201:enzymology*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D051381:Rats
D005296:Ferrous Compounds; C099547:verdoheme; D006418:Heme; D015786:Cytochromes b5