The number and localisation of adenine nucleotide-binding sites in beef-heart mitochondrial ATPase (F1) determined by photolabelling with 8-azido-ATP and 8-azido-ADP.
1. When irradiated 8-azido-ATP becomes covalently bound (as the nitreno compound) to beef-heart mitochondrial ATPase (F1) as the triphosphate, either in the absence or presence of Mg2+, label covalently bound is not hydrolysed. 2. In the presence of Mg2+ the nitreno-ATP is bound to both the alpha and beta subunits, mainly (63%) to the alpha subunits. 3. After successive photolabelling of F1 with 8-azido-ATP (no Mg2+) and 8-azido-ADP (with Mg2+) 4 mol label is bound to F1, 2 mol to the alpha and 2 mol to the beta subunits. 4. When the order of photolabelling is reversed, much less 8-nitreno-ATP is bound to F1 previously labelled with 8-nitreno-ADP. It is concluded that binding to the alpha-subunits hinders binding to the beta subunits. 5. F1 that has been photolabelled with up to 4 mol label still contains 2 mol firmly bound adenine nucleotides per mol F1. 6. It is concluded that at least 6 sites for adenine nucleotides are present in isolated F1.
D000227:Adenine Nucleotides / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000528:radiation effects; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000528:radiation effects; D000818:Animals; D001386:Azides; D001665:Binding Sites; D002417:Cattle; D004586:Electrophoresis; D008274:Magnesium / Q000494:pharmacology; D008929:Mitochondria, Heart / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D006180:Proton-Translocating ATPases
D000227:Adenine Nucleotides; D001386:Azides; D010761:Phosphorus Radioisotopes; C017040:8-azidoadenosine 5'-triphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases; C021622:8-azidoadenosine diphosphate; D008274:Magnesium