Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volume 1757, Issue 9-10, Pages 1155-1161Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbabio.2006.04.016
Keywords
NADH : ubiquinone oxidoreductase; respiratory Complex I; active/de-active transition; sulfhydryl group; mitochondria
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Funding
- FIC NIH HHS [1R03TW006041, R03 TW007825-01, R03 TW006041] Funding Source: Medline
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The spatial arrangement and chemical reactivity of the activation-dependent thiol in the mitochondrial Complex I was studied using the membrane penetrating N-ethylmaleimide (NEM) and non-penetrating anionic 5,5'-dithiobis-(2-nitrobenzoate) (DTNB) as the specific inhibitors of the enzyme in mitochondria and inside-out submitochondrial particles (SMP). Both NEM and DTNB rapidly inhibited the de-activated Complex I in SMP. In mitochondria NEM caused rapid inhibition of Complex I, whereas the enzyme activity was insensitive to DTNB. In the presence of the channel-forming antibiotic alamethicin, mitochondrial Complex I became sensitive to DTNB. Neither active nor de-activated Complex I in SMP was inhibited by oxidized glutathione (10 mM, pH 8.0, 75 min). The data suggest that the active/de-active transition sulfhydryl group of Complex I which is sensitive to inhibition by NEM is located at the inner membrane-matrix interface. These data include the sidedness dependency of inhibition, effect of pH, ionic strength, and membrane bilayer modification on enzyme reactivity towards DTNB and its neutral analogue. (c) 2006 Elsevier B.V. All rights reserved.
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