Thiol-based Oxidative Posttranslational Modifications (OxiPTMs) of Plant Proteins

Abstract

The thiol group of cysteine (Cys) residues, often present in the active center of the protein, is of particular importance to protein function, which is significantly determined by the redox state of a protein's environment. Our knowledge of different thiol-based oxidative posttranslational modifications (oxiPTMs), which compete for specific protein thiol groups, has increased over the last 10 years. The principal oxiPTMs include S-sulfenylation, S-glutathionylation, S-nitrosation, persulfidation, S-cyanylation and S-acylation. The role of each oxiPTM depends on the redox cellular state, which in turn depends on cellular homeostasis under either optimal or stressful conditions. Under such conditions, the metabolism of molecules such as glutathione, NADPH (reduced nicotinamide adenine dinucleotide phosphate), nitric oxide, hydrogen sulfide and hydrogen peroxide can be altered, exacerbated and, consequently, outside the cell's control. This review provides a broad overview of these oxiPTMs under physiological and unfavorable conditions, which can regulate the function of target proteins.

Keywords: S-cyanylation and S-acylation; S-glutathionylation; S-nitrosation; S-sulfenylation; Persulfidation.

Fig. 1

Outline of the main thiol-based oxiPTMs. The upper side of the panel indicates the oxidation states of sulfur (S) in proteins, which can be from thiol (−2) to sulfonic acid (+4). Under cellular oxidant conditions, the oxidation from sulfinic acid to sulfonic acid could take place, the latter being an irreversible process. The principal reversible oxiPTMs result from the interaction between thiolate with either hydrogen peroxide (H₂O₂; S-sulfenylation); glutathione (GSH; S-glutathionylation), nitric oxide (NO; S-nitrosation), hydrogen sulfide (H₂S; persulfidation), cyanide (HCN; S-cyanylation) or fatty acid (FA; S-acylation) are also displayed in the lower side of the panel.

Fig. 2

Comparative analysis of the number of proteins identified that could be potentially targeted by one of the main thiol-based oxiPTMs in the model plant Arabidopsis thaliana. These PTMs include 2643 proteins for S-acylation (Kumar et al. 2020), 163 for S-cyanylation (García et al. 2019), 2015 for persulfidation (Aroca et al. 2017), 926 for S-nitrosation (Hu et al. 2015), 79 for S-glutathionylation (Dixon et al. 2005) and 1394 for S-sulfenylation (Huang et al. 2019)