The Dual-Targeted Plant Sulfiredoxin Retroreduces the Sulfinic Form of Atypical Mitochondrial Peroxiredoxin  

Abstract

Sulfiredoxin (Srx) couples the energy of ATP hydrolysis to the energetically unfavorable process of reducing the inactive sulfinic form of 2-cysteine peroxiredoxins (Prxs) to regenerate its active form. In plants, Srx as well as typical 2-cysteine Prx have been considered as enzymes with exclusive chloroplast localization. This work explores the subcellular localization of Srx in pea (Pisum sativum) and Arabidopsis (Arabidopsis thaliana). Immunocytochemistry, analysis of protein extracts from isolated intact organelles, and cell-free posttranslational import assays demonstrated that plant Srx also localizes to the mitochondrion in addition to plastids. The dual localization was in line with the prediction of a signal peptide for dual targeting. Activity tests and microcalorimetric data proved the interaction between Srx and its mitochondrial targets Prx IIF and thioredoxin. Srx catalyzed the retroreduction of the inactive sulfinic form of atypical Prx IIF using thioredoxin as reducing agent. Arabidopsis Srx also reduced overoxidized human Prx V. These results suggest that plant Srx could play a crucial role in the regulation of Prx IIF activity by controlling the regeneration of its overoxidized form in mitochondria, which are sites of efficient reactive oxygen species production in plants.

Cysteine–based redox regulation and signaling in plants

“…While SO 2 H are mostly irreversible oxidation forms, an enzyme called sulfiredoxin (Srx) is able to catalyze the ATP-dependent reduction of the SO 2 H formed on these sensitive 2-Cys Prxs (Biteau et al, 2003). This mechanism is likely valid for plants as a Srx, dual-targeted to chloroplasts and mitochondria, can specifically reduce SO 2 H formed on 2-Cys Prxs but also on plant PrxII or mammalian PrxV (Rey et al, 2007; Iglesias-Baena et al, 2010, 2011). Interestingly, the SO 2 H reduction proceeds via the formation of a phosphoryl intermediate on the sulfinyl moiety, attacked by the catalytic cysteine of Srx finally forming a thiosulfinate intermediate between Prx and Srx (Jonsson et al, 2008; Roussel et al, 2008).…”

Lack of mitochondrial thioredoxin o1 is compensated by antioxidant components under salinity in Arabidopsis thaliana plants

“…A pea TRX o 1 was later described to be present in mitochondria and nuclei where it regulates several processes as respiration and cell cycle progression through its interaction with target proteins as alternative oxidase (AOX) or proliferating cellular nuclear antigen among others (Martí et al , Calderón et al ). In mitochondria, a strong interaction occurs between PsTRX o 1 and peroxiredoxin IIF (PsPRXIIF), which together with sulfiredoxin, may constitute the mitochondria redox system (Barranco‐Medina et al , Iglesias‐Baena et al ). Further analysis showed that additional mitochondrial proteins are targets of TRX o 1, suggesting that it may also control their redox status (Martí et al, ).…”

VDAC3 As a Potential Marker of Mitochondrial Status Is Involved in Cancer and Pathology

“…The results showed that (i) VDAC3 is electrophoretically heterogeneous (i.e., it is present with different mobility in SDS-PAGE) because the arrangement of oxidized cysteine is different in the various bands; (ii) different molecules contain different extents, in terms of type and quantity, of oxidized cysteine (we like to call them: “redox isomers”); (iii) the oxidation states of the cysteine are not random but some of them (Cysteines 2 and 8) are always found in a reduced (exactly derivatized by iodoacetamide) state, others (Cysteines 36, 65, and 229) in different oxidation levels (+1, +3, and +5); (iv) the oxidation to sulfinic (+3) or sulfonic (+5) acid is biologically irreversible. The only known reductase is thioredoxin/sulforedoxin system that targets sulfinic cysteine (48, 49), while there are no known enzymes able to reverse the sulfonic acid (+5) whose function is unknown and possibly related to either modify the protein electrostatic equilibrium or target it for degradation.…”