Characterization of the iron-sulfur protein of the mitochondrial outer membrane partially purified from beef kidney cortex.
The iron-sulfur protein present in the mitochondrial outer membrane has been partially purified from beef kidney cortex mitochondria by means of selective solubilization followed by DEAE-cellulose chromatography. The EPR spectrum of the iron-sulfur protein with g-values at 2.01, 1.94 and 1.89 was well resolved up to 200 K which is unusual for an iron-sulfur protein. Analyses confirmed a center with two iron and two labile sulfur atoms in the protein. By measuring the effect of oxidation-reduction potential on the EPR signal amplitude, midpoint potentials at pH 7.2 were determined both for the purified iron-sulfur protein, +75 (+/- 5) mV, and in prepared mitochondrial outer membrane, +62 (+/- 6) mV. At pH 8.2 slightly lower values were indicated, +62 and 52 mV, respectively. The oxidation-reduction equilibrium involved a one electron transfer. A functional relationship to the rotenone-insensitive NADH-cytochrome c oxidoreductase in the mitochondrial outer membrane is suggested. Both this activity and the iron-sulfur center were sensitive to acidities slightly below pH 7 in contrast to the iron-sulfur centers of the inner membrane.
D000818:Animals; D002417:Cattle; D003579:Cytochrome Reductases / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D007506:Iron-Sulfur Proteins / Q000302:isolation & purification* / Q000378:metabolism; D007672:Kidney Cortex / Q000648:ultrastructure; D008565:Membrane Proteins / Q000302:isolation & purification; D008667:Metalloproteins / Q000302:isolation & purification*; D008928:Mitochondria / Q000032:analysis* / Q000648:ultrastructure; D010084:Oxidation-Reduction; D013053:Spectrophotometry
D007506:Iron-Sulfur Proteins; D008565:Membrane Proteins; D008667:Metalloproteins; D003579:Cytochrome Reductases