The chromone inhibitor stigmatellin--binding to the ubiquinol oxidation center at the C-side of the mitochondrial membrane.
Stigmatellin, a chromone inhibitor acting at the Q0 center of the bc1 complex, binds to the heme b-566 domain of cytochrome b as well as to the Fe2S2 protein. Its binding induces a shift of the alpha-band of heme b-566 to 568 nm. It does not influence the ligand field of the heme b-562 center. Concomitant with the red shift, stigmatellin gives rise to an alteration of the EPR line shape of the Fe2S2 cluster, namely linewidth narrowing and g value shifts at all 3 principal values. The midpoint redox potential of the Fe2S2 protein is shifted from 290 to 540 mV.
von Jagow
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Ohnishi
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D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002417:Cattle; D004578:Electron Spin Resonance Spectroscopy; D014450:Electron Transport Complex III; D007425:Intracellular Membranes / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D008689:Methacrylates; D008928:Mitochondria / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism; D010084:Oxidation-Reduction; D011090:Polyenes / Q000378:metabolism; D011485:Protein Binding; D011808:Quinone Reductases / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000378:metabolism
D007506:Iron-Sulfur Proteins; D008689:Methacrylates; D009097:Multienzyme Complexes; D011090:Polyenes; C037989:Rieske iron-sulfur protein; D013844:Thiazoles; D014451:Ubiquinone; C030517:myxothiazol; C041573:stigmatellin; D011808:Quinone Reductases; D014450:Electron Transport Complex III; C003741:ubiquinol