Physiological levels of mammalian uncoupling protein 2 do not uncouple yeast mitochondria.

TitlePhysiological levels of mammalian uncoupling protein 2 do not uncouple yeast mitochondria.
Publication TypeJournal Article
Year of Publication2001
AuthorsStuart, JA, Harper, JA, Brindle, KM, Jekabsons, MB, Brand, MD
JournalJ Biol Chem
Volume276
Issue21
Pagination18633-9
Date Published2001 May 25
ISSN0021-9258
KeywordsGene Expression Regulation, Humans, Ion Channels, Membrane Transport Proteins, Mitochondria, Mitochondrial Proteins, Proteins, Saccharomyces cerevisiae, Uncoupling Protein 2
Abstract

We assessed the ability of human uncoupling protein 2 (UCP2) to uncouple mitochondrial oxidative phosphorylation when expressed in yeast at physiological and supraphysiological levels. We used three different inducible UCP2 expression constructs to achieve mitochondrial UCP2 expression levels in yeast of 33, 283, and 4100 ng of UCP2/mg of mitochondrial protein. Yeast mitochondria expressing UCP2 at 33 or 283 ng/mg showed no increase in proton conductance, even in the presence of various putative effectors, including palmitate and all-trans-retinoic acid. Only when UCP2 expression in yeast mitochondria was increased to 4 microg/mg, more than an order of magnitude greater than the highest known physiological concentration, was proton conductance increased. This increased proton conductance was not abolished by GDP. At this high level of UCP2 expression, an inhibition of substrate oxidation was observed, which cannot be readily explained by an uncoupling activity of UCP2. Quantitatively, even the uncoupling seen at 4 microgram/mg was insufficient to account for the basal proton conductance of mammalian mitochondria. These observations suggest that uncoupling of yeast mitochondria by UCP2 is an overexpression artifact leading to compromised mitochondrial integrity.

DOI10.1074/jbc.M011566200
Alternate JournalJ. Biol. Chem.
Citation Key10.1074/jbc.M011566200
PubMed ID11278935