Open AccessEffect of Funiculosin and Antimycin A on the Redox‐Driven H + ‐Pumps in Mitochondria: on the Nature of ‘Leaks’
Author(s) -
PIETROBON Daniela,
AZZONE Giovanni F.,
WALZ Dieter
Publication year - 1981
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1981.tb06350.x
Subject(s) - antimycin a , malonate , electron transfer , electron transport chain , redox , chemistry , respiratory chain , electrochemistry , biophysics , mitochondrion , inorganic chemistry , photochemistry , biochemistry , electrode , biology
The effect of antimycin A and funiculosin, two inhibitors which block electron transfer in the b‐c 1 complex, on electron flow and electrochemical potential difference of H + ions in mitochondria at static head (state 4) is investigated. In addition, the respiratory control ratio is determined as the ratio between uncoupler stimulated and static‐head electron flow. Malonate, a competitive inhibitor of succinic dehydrogenase, is used for comparison. All three inhibitors cause an extensive depression of static‐head electron flow but only a limited decrease in the electrochemical potential difference of H + ions. With the antimycin‐type of inhibitors, the respiratory control ratio slightly increases up to about 50% inhibition of electron flow and then steeply declines. With malonate, a strong decrease of the respiratory control ratio is observed in a concentration range where the electron flow is inhibited less than 10%. It is shown that the data do not compiy with the generally accepted hypothesis of a leak conductance being regulated by the electrochemical potential difference of H + ions. They can be interpreted in terms of not tightly coupled redox‐driven H + ‐pumps. A non‐vanishing electron flow at static head then arises predominantly from molecular slipping in the pumps, and the (constant) leak conductance yields only a minor contribution.