Cysteine residues exposed on protein surfaces are the dominant intramitochondrial thiol and may protect against oxidative damage.

TitleCysteine residues exposed on protein surfaces are the dominant intramitochondrial thiol and may protect against oxidative damage.
Publication TypeJournal Article
Year of Publication2010
AuthorsRequejo, R, Hurd, TR, Costa, NJ, Murphy, MP
JournalFEBS J
Date Published2010 Mar
KeywordsAnimals, Cells, Cultured, Cysteine, Glutathione, Membrane Proteins, Mitochondria, Heart, Mitochondria, Liver, Oxidative Stress, Rats, Sulfhydryl Compounds

Cysteine plays a number of important roles in protecting the cell from oxidative damage through its thiol functional group. These defensive functions are generally considered to be carried out by the low molecular weight thiol glutathione and by cysteine residues in the active sites of proteins such as thioredoxin and peroxiredoxin. In addition, there are thiols exposed on protein surfaces that are not directly involved with protein function, although they can interact with the intracellular environment. In the present study, in subcellular fractions prepared from rat liver or heart, we show that the quantitatively dominant free thiols are those of cysteine residues exposed on protein surfaces and not those carried by glutathione. Within the mitochondrial matrix, the concentration of exposed protein thiols is 60-90 mm, which is approximately 26-fold higher than the glutathione concentration in that compartment. This suggests that exposed protein thiols are of greater importance than glutathione for nonenzyme catalysed reactions of thiols with reactive oxygen and nitrogen species and with electrophiles within the cell. One such antioxidant role for exposed protein thiols may be to prevent protein oxidative damage. In the present study, in mitochondrial membranes and in complex I, we show that exposed protein thiols protect against tyrosine nitration and protein dysfunction caused by peroxynitrite. Therefore, exposed protein thiols are the dominant free thiol within the cell and may play a critical role in intracellular antioxidant defences against oxidative damage.

Alternate JournalFEBS J.
Citation Key10.1111/j.1742-4658.2010.07576.x
PubMed ID20148960
PubMed Central IDPMC2847196
Grant ListMC_U105663142 / / Medical Research Council / United Kingdom