Section 5
Chapter 4,862

Brown adipose tissue mitochondria the regulation of the 32000 molecular weight uncoupling protein by fatty acids and purine nucleotides

Rial, E.; Poustie, A.; Nicholls, D.G.

European Journal of Biochemistry 137(1-2): 197-204


ISSN/ISBN: 0014-2956
Accession: 004861651

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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 32,000-MW uncoupling protein. Fatty acids lower the affinity of nucleotide binding to the 32,000-MW 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 nulcoetide by lowering the break-point at which the conductance of the 32,000-MW protein increases. Fatty acids have no effect on the chloride uniport activity of the 32,000-MW protein, but decouple the interference between chloride and protons when the simultaneous transport of both ions is attempted.

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