molecular oxygen associated to the generation of an electrochemical membrane potential available for ATP synthesis. The electron transport pathway activated by exogenous cyto-c molecules is completely distinct from the one catalyzed by the respiratory chain. Dextran sulfate (500 kDa), known to interact with porin (the voltage-dependent anion channel), other than to inhibit the release of ATP synthesized inside the mitochondria, greatly decreases the activity of exogenous NADH/cyto-c system of intact mitochondria but has no eVect on the reconstituted system made of mitoplasts and external membrane preparations. The results obtained are consistent with the existence of speciWc contact sites containing cytochrome oxidase and porin, as components of the inner and the outer membrane respectively, involved in the oxidation of cytosolic NADH. The proposal is put forward that the bi-trans-membrane electron transport chain activated by cytosolic cyto-c becomes, in physio-pathological conditions: (i) functional in removing the excess of cytosolic NADH; (ii) essential for cell survival in the presence of an impairment of the Wrst three respiratory complexes; and (iii) an additional source of energy at the beginning of apoptosis.
Porin and cytochrome oxidase containing contact sites involved in the oxidation of cytosolic NADH
LA PIANA, Gianluigi;
2005-01-01
Abstract
molecular oxygen associated to the generation of an electrochemical membrane potential available for ATP synthesis. The electron transport pathway activated by exogenous cyto-c molecules is completely distinct from the one catalyzed by the respiratory chain. Dextran sulfate (500 kDa), known to interact with porin (the voltage-dependent anion channel), other than to inhibit the release of ATP synthesized inside the mitochondria, greatly decreases the activity of exogenous NADH/cyto-c system of intact mitochondria but has no eVect on the reconstituted system made of mitoplasts and external membrane preparations. The results obtained are consistent with the existence of speciWc contact sites containing cytochrome oxidase and porin, as components of the inner and the outer membrane respectively, involved in the oxidation of cytosolic NADH. The proposal is put forward that the bi-trans-membrane electron transport chain activated by cytosolic cyto-c becomes, in physio-pathological conditions: (i) functional in removing the excess of cytosolic NADH; (ii) essential for cell survival in the presence of an impairment of the Wrst three respiratory complexes; and (iii) an additional source of energy at the beginning of apoptosis.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
