Reconstitution of novel mitochondrial uncoupling proteins, human UCP2 and UCP3, expressed in yeast, was performed to characterize fatty acid (FA)-induced H+ efflux in the resulted proteoliposomes. We now demonstrate for the first time that representatives of physiologically abundant long chain FAs, saturated or unsaturated, activate H+ translocation in UCP2- and UCP3-proteoliposomes. Efficiency of lauric, palmitic or linoleic acid was roughly the same, but oleic acid induced faster H+ uniport. We have confirmed that ATP and GTP inhibit such FA-induced H+ uniport mediated by UCP2 and UCP3. Coenzyme Q10 did not further significantly activate the observed H+ efflux. In conclusion, careful instant reconstitution yields intact functional recombinant proteins, UCP2 and UCP3, the activity of which is comparable with UCP1.

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