Transport of anions and protons by the mitochondrial uncoupling protein and its regulation by nucleotides and fatty acids. A new look at old hypotheses
The uncoupling protein generates heat by catalyzing electrophoretic proton transport across the inner membrane of brown adipose tissue mitochondria. It also transports Cl- and other monovalent anions, and both proton and anion transport are inhibited by purine nucleotides. Several long-standing hypo...
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Veröffentlicht in: | The Journal of biological chemistry 1994-10, Vol.269 (42), p.26184-26190 |
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Sprache: | eng |
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Zusammenfassung: | The uncoupling protein generates heat by catalyzing electrophoretic proton transport across the inner membrane of brown adipose
tissue mitochondria. It also transports Cl- and other monovalent anions, and both proton and anion transport are inhibited
by purine nucleotides. Several long-standing hypotheses bear on specific aspects of Cl- transport, H+ transport, and nucleotide
gating mechanisms in uncoupling protein. We reevaluated these hypotheses in mitochondria and liposomes reconstituted with
purified uncoupling protein; GDP inhibition is strictly noncompetitive with Cl- and unaffected by either transmembrane electrical
potential or fatty acids. The Km and Vmax values for Cl- are independent of pH, arguing against a common binding site for
Cl- and OH- ions. Cl- transport was inhibited by fatty acids and stimulated by fatty acid removal, refuting the consensus
hypothesis that there is no interaction between fatty acids and anion transport through uncoupling protein. These results
support a mechanism in which the transport pathway for anions is identical with the fatty acid binding site and distinct from
the nucleotide binding site. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/S0021-9258(18)47176-1 |