期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 278, 期 23, 页码 20761-20769出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M212850200
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Human UCP2 and UCP3, expressed in yeast, were studied to establish their high affinity regulatory ligands. UCPn were reconstituted into liposomes and assayed for fatty acid (FA)-induced H+ efflux. All natural long chain FAs activated UCP2- and UCP3-mediated H+ translocation. Coenzyme Q(10) had no further significant activating effect. Evaluated parameters of FA activation (FA cycling) kinetics revealed the highest apparent affinity to UCP2 ( the lowest K-m values: 20 and 29 muM, respectively) for omega-6 polyunsaturated FAs (PUFAs), all-cis-8,11,14-eicosatrienoic and all-cis-6,9,12-octadecatrienoic acids, which are also the most potent agonists of the nuclear PPARbeta receptor in the activation of UCP2 transcription. omega-3 PUFA, cis-5,8,11,14,17-eicosapentaenoic acid had lower affinity (K-m, 50 muM), although as an omega-6 PUFA, arachidonic acid exhibited the same low affinity as lauric acid (K-m, similar to200 muM). These findings suggest a possible dual role of some PUFAs in activating both UCPn expression and uncoupling activity. UCP2 (UCP3)-dependent H+ translocation activated by all tested FAs was inhibited by purine nucleotides with apparent affinity to UCP2 (reciprocal K-i) decreasing in order: ADP>ATPsimilar toGTP>GDPmuch greater thanAMP. Also [H-3] GTP ([H-3] ATP) binding to isolated Escherichia coli (K-d, similar to5 muM) or yeast-expressed UCP2 (K-d, similar to1.5 muM) or UCP3 exhibited high affinity, similar to UCP1. The estimated number of [H-3] GTP high affinity (K-d, <0.4 mu M) binding sites was (in pmol/mg of protein) 182 in lung mitochondria, 74 in kidney, 28 in skeletal muscle, and similar to 20 in liver mitochondria. We conclude that purine nucleotides must be the physiological inhibitors of UCPn-mediated uncoupling in vivo.
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