Brown-adipose-tissue mitochondria: the regulation of the 32000-Mr uncoupling protein by fatty acids and purine nucleotides.
The increased proton permeability induced by the addition of a synthetic proton translocator to non-respiring hamster brown-fat mitochondria is unaffected by purine nucleotide addition. In contrast the permeability induced by fatty acids is inhibited by nucleotide, indicating that fatty acids act at the 32000-Mr uncoupling protein. Fatty acids lower the affinity of nucleotide binding to the 32000-Mr protein, but not sufficiently to explain their uncoupling action. The sensitivity of the fatty acid modulation of permeability is dependent on chain length, extent of unsaturation and pH. There is a requirement for an unesterified carboxyl group. In respiring mitochondria fatty acids act in the presence of nucleotide by lowering the 'break-point' potential at which the conductance of the 32000-Mr protein increases. Fatty acids have no effect on the chloride uniport activity of the 32000-Mr protein, but decouple the interference between chloride and protons when the simultaneous transport of both ions is attempted.
D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000818:Animals; D002712:Chlorides / Q000378:metabolism; D006224:Cricetinae; D005227:Fatty Acids / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008564:Membrane Potentials; D008647:Mesocricetus; D008928:Mitochondria / Q000378:metabolism*; D010101:Oxygen Consumption; D010539:Permeability; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D011522:Protons; D011685:Purine Nucleotides / Q000378:metabolism*; D014475:Uncoupling Agents
D002712:Chlorides; D005227:Fatty Acids; D011506:Proteins; D011522:Protons; D011685:Purine Nucleotides; D014475:Uncoupling Agents