REVERSAL OF ELECTRON TRANSFER IN THE RESPIRATORY CHAIN 1 37 



Klingenberg : We are also investigating the effects of ATP on the respiratory 

 chain. This research started with the ATP-dependent DFX reduction. The latest 

 results, which I shall show later in the afternoon, have shown that ATP can also 

 interact at the cytochrome region under aerobic conditions. We can induce 

 respiratory control and by this get a cross-over point. Cytochrome b is further 

 reduced and cytochrome c is further oxidized. We do not see a further oxidation of 

 flavoprotein. Flavoprotein, cytochrome b and DFX are all reduced on the addition 

 of ATF, and cytochrome c, in a very fast reaction, is oxidized. We believe that this 

 signifies the interaction of ATF at the phosphorylation step between cytochrome h 

 and cytochrome c and the skeletal muscle mitochondria are thus brought from a 

 slightly uncoupled state to a coupled state by the addition of ATF. 



Chance: Just a question. Is oxygen present ? 



Klingenberg : Yes. 



Ch.'XNCe: Well that is very interesting, because it is much more difficult to 

 reverse electron transfer in the cytochrome region when oxygen is present than 

 when oxygen is not present. 



Klingenberg : This was at the initiation of state 4. 



