Intraliposomal nucleotides change the kinetics of reconstituted cytochrome c oxidase from bovine heart but not from Paracoccus denitrificans.
Isolated cytochrome c oxidases of P. denitrificans and bovine heart were reconstituted in liposomes and the kinetics of cytochrome c oxidation were measured in the presence and absence of nucleotides either inside or outside of proteoliposomes, and after photolabelling with 8-azido-ATP. Intraliposomal ATP increases and ADP decreases the kinetics of ferrocytochrome c oxidation of the bovine but not of the Paracoccus enzyme. Extra-liposomal ATP and ADP increase the Km for cytochrome c of both enzymes, but ATP acts at lower concentrations than ADP. The increase of the Km for cytochrome c is obtained in coupled as well as in uncoupled proteoliposomes. Photolabelling with 8-azido-ATP of the reconstituted Paracoccus enzyme also increases the Km for cytochrome c which is completely prevented if ATP but not if ADP is present during illumination as was found with reconstituted cytochrome c oxidase from bovine heart. The data suggest a specific interaction of ATP and ADP with nuclear-coded subunits of bovine heart cytochrome c oxidase from the matrix side, because the effects are not found with the Paracoccus enzyme, which lacks these subunits.
Hüther
F J
FJ
Biochemie, Fb Chemie der Philipps-Universität, Marburg, F.R.G.
Kadenbach
B
B
D000227:Adenine Nucleotides / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives; D000345:Affinity Labels; D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D008081:Liposomes; D046911:Macromolecular Substances; D009206:Myocardium / Q000201:enzymology*; D010231:Paracoccus denitrificans / Q000201:enzymology*
D000227:Adenine Nucleotides; D000345:Affinity Labels; D008081:Liposomes; D046911:Macromolecular Substances; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV