We investigated the occurrence of the plant Uncoupling Protein (UCP) in mitochondria isolated from both fresh (f-JAM) and aged-dehydrated (a-d-JAM) slices of Jerusalem artichoke tubers (Helianthus tuberosus L.). The presence of UCP was shown by immunological analysis and its function was investigated by measuring the decrease of the mitochondrial membrane potential due to linoleic acid (LA) and its inhibition by purine nucleotides under conditions in which the adenine nucleotide translocator (ANT) was inhibited by atractyloside (Atr). f-JAM and a-d-JAM had the same protein content, but differed from one another with respect to purine nucleotide inhibition, substrate specificity, and sensitivity to ROS. Hydrogen peroxide and superoxide anion, generated in situ by xanthine plus xanthine oxidase, caused a significant increase in the UCP function in a-d-JAM, but not in f-JAM. This occurred in a manner sensitive to ATP, but not to Atr, thus showing that ANT has no role in the process. The dependence of the rate of membrane potential decrease on increasing LA concentrations, either in the absence or the presence of ROS, showed a sigmoidal saturation both in f-JAM and a-d-JAM. However, addition of ROS in a-d-JAM resulted in about 40% increase of the V max value, with no change in the K 0.5 (about 20 μM), whereas in f-JAM no effect on either the V max or K 0.5 (about 28 μM) was found. Furthermore, a decreased ROS production as a result of LA addition was found in both f-JAM and a-d-JAM, the effect being more marked in a-d-JAM. © 2005 Elsevier SAS. All rights reserved.

Plant uncoupling protein in mitochondria from aged-dehydrated slices of Jerusalem artichoke tubers becomes sensitive to superoxide and to hydrogen peroxide without increase in protein level

PASTORE, DONATO;
2006-01-01

Abstract

We investigated the occurrence of the plant Uncoupling Protein (UCP) in mitochondria isolated from both fresh (f-JAM) and aged-dehydrated (a-d-JAM) slices of Jerusalem artichoke tubers (Helianthus tuberosus L.). The presence of UCP was shown by immunological analysis and its function was investigated by measuring the decrease of the mitochondrial membrane potential due to linoleic acid (LA) and its inhibition by purine nucleotides under conditions in which the adenine nucleotide translocator (ANT) was inhibited by atractyloside (Atr). f-JAM and a-d-JAM had the same protein content, but differed from one another with respect to purine nucleotide inhibition, substrate specificity, and sensitivity to ROS. Hydrogen peroxide and superoxide anion, generated in situ by xanthine plus xanthine oxidase, caused a significant increase in the UCP function in a-d-JAM, but not in f-JAM. This occurred in a manner sensitive to ATP, but not to Atr, thus showing that ANT has no role in the process. The dependence of the rate of membrane potential decrease on increasing LA concentrations, either in the absence or the presence of ROS, showed a sigmoidal saturation both in f-JAM and a-d-JAM. However, addition of ROS in a-d-JAM resulted in about 40% increase of the V max value, with no change in the K 0.5 (about 20 μM), whereas in f-JAM no effect on either the V max or K 0.5 (about 28 μM) was found. Furthermore, a decreased ROS production as a result of LA addition was found in both f-JAM and a-d-JAM, the effect being more marked in a-d-JAM. © 2005 Elsevier SAS. All rights reserved.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11369/204551
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