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.[1]References
- Intraliposomal nucleotides change the kinetics of reconstituted cytochrome c oxidase from bovine heart but not from Paracoccus denitrificans. Hüther, F.J., Kadenbach, B. Biochem. Biophys. Res. Commun. (1988) [Pubmed]
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