Specific effects of ATP on the kinetics of reconstituted bovine heart cytochrome-c oxidase.
Bovine heart cytochrome-c oxidase was reconstituted in liposomes and the kinetics of cytochrome c oxidation were measured by the polarographic and photometric method under uncoupled conditions in the presence of various polyvalent anions. In order to distinguish between specific and unspecific ionic effects of ATP, the photolabelling reagent 8-azido-ATP was applied. Covalently bound ATP at the enzyme complex caused the same increase of Km for cytochrome c as free ATP, if measured by the photometric assay. The increase of Km by photolabelling with 8-azido-ATP was completely prevented by ATP, but not by ADP. The data indicate the occurrence of a specific binding site for ATP at the cytosolic side of cytochrome-c oxidase, which, after binding of ATP, changes the kinetics of cytochrome c oxidation.
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000345:Affinity Labels; D000818:Animals; D001386:Azides; D002417:Cattle; D003576:Electron Transport Complex IV / Q000032:analysis*; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology*; D010710:Phosphates / Q000494:pharmacology
D000345:Affinity Labels; D001386:Azides; D010710:Phosphates; C017040:8-azidoadenosine 5'-triphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV