Brown-adipose-tissue mitochondria: photoaffinity labelling of the regulatory site of energy dissipation.
Brown-adipose-tissue mitochondria possess an energy-dissipating ion uniport which is inhibited by purine nucleotides. The regulatory nucleotides bind to a high-affinity site on the outer face of the inner membrane which is independent of the adenine nucleotide translocator. A direct correlation between affinity for the regulatory site and ability to inhibit the ion uniport is demonstrated for a number of nucleotide analogues. 8-Azido-adenosine 5'-triphosphate, a photoaffinity label, also competes with GDP for the binding site and induces respiratory control. 8-Azido-adenosine [gamma-32P]triphosphate was prepared and covalently bound to hamster brown-adipose-tissue mitochondria by near-ultraviolet irradiation. Two major radioactive bands were identified of apparent molecular weight 30000 and 32000, representing 6% and 10% of the inner membrane protein respectively. Selective labelling enabled the 30000-Mr protein to be identified as the carboxyatractylate binding component of the adenine-nucleotide translocator and the 32000-Mr protein to be identified as the regulatory site of the energy-dissipating ion uniport. The levels of the 32000-Mr protein in the inner membrane of guinea-pig brown-adipose-tissue mitochondria correlate with the degree of thermogenic adaptation of the animal.
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000345:Affinity Labels; D000818:Animals; D001665:Binding Sites; D006224:Cricetinae; D006153:Guanosine Diphosphate / Q000494:pharmacology; D006168:Guinea Pigs; D008647:Mesocricetus; D008928:Mitochondria / Q000378:metabolism*; D008970:Molecular Weight; D010101:Oxygen Consumption / Q000187:drug effects*; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism
D000345:Affinity Labels; D011506:Proteins; D006153:Guanosine Diphosphate; D000255:Adenosine Triphosphate