Complex I and complex III of mitochondria have common inhibitors acting as ubiquinone antagonists.


Degli Esposti, M; Ghelli, A; Crimi, M; Estornell, E; Fato, R; Lenaz, G

Publication Year 1993
Journal Biochemical and Biophysical Research Communications
Pages 1090-1096
Volume 190
Issue 3
PMID 8439309.0
DOI 10.1006/bbrc.1993.1161

Mitochondrial complex I and complex III have common inhibitors with ubiquinone-like structure. The tridecyl analog of stigmatellin, which inhibits mitochondrial complex III at nanomolar concentrations, also inhibits the NADH:ubiquinone reductase activity of complex I at micromolar concentrations. The inhibitor titer depends upon the concentration of the mitochondrial particles and extrapolates to 0.2 microM at zero particle concentration. The stigmatellin analog is more powerful than its parent compound and is noncompetitive with exogenous ubiquinones, rotenone and piericidin. Myxothiazol, which is another potent inhibitor of complex III, is also found to inhibit the activity of complex I with a titer comparable to that of the tridecyl analog of stigmatellin. Additionally, piericidin, which is the most powerful inhibitor of complex I, inhibits the ubiquinol:cytochrome c reductase activity of complex III at micromolar concentrations in mitochondrial particles and at submicromolar concentrations in the isolated enzyme complex.