Sensitivity of plant mitochondrial terminal oxidases to the lipid peroxidation product 4-hydroxy-2-nonenal (HNE)

摘要

pWe have investigated the effect of the lipid peroxidation product, HNE (4-hydroxy-2-nonenal), on plant mitochondrial electron transport. In mitochondria isolated from iArabidopsis thaliana/i cell cultures, HNE inhibited succinate-dependent oxygen consumption via the Aox (alternative oxidase), but had minimal effect on respiration via Cox (cytochrome ic/i oxidase). Maximal Cox activity, measured with reduced cytochrome ic/i as substrate, was only slightly inhibited by high concentrations of HNE, at which Aox was completely inhibited. Incubation with HNE prevented dimerization of the Aox protein, suggesting that one site of modification was the conserved cysteine residue involved in dimerization and activation of this enzyme (CyssubI/sub). However, a naturally occurring isoform of Aox lacking CyssubI/sub and unable to be dimerized, iLe/iAox1b from tomato (iLycopersicon esculentum/i), was equally sensitive to HNE inhibition, showing that other amino acid residues in Aox also interact with HNE. The presence of HNE iin vivo/i in iArabidopsis/i cell cultures was also investigated. Induction of oxidative stress in the cell cultures by the addition of hydrogen peroxide, antimycin A or menadione, caused a significant increase in hydroxyalkenals (of which HNE is the most prominent). Western blotting of mitochondrial proteins with antibodies against HNE adducts, demonstrated significant modification of proteins during these treatments. The implications of these results for the response of plants to reactive oxygen species are discussed./p