Abstract
Tyrosine-specific protein tyrosine phosphatases (Tyr-specific PTPases) are key signaling enzymes catalyzing the removal of the phosphate group from phosphorylated tyrosine residues on target proteins. This post-translational modification notably allows the regulation of mitogen-activated protein kinase (MAPK) cascades during defense reactions. Arabidopsis thaliana protein tyrosine phosphatase 1 (AtPTP1), the only Tyr-specific PTPase present in this plant, acts as a repressor of H2O2 production and regulates the activity of MPK3/MPK6 MAPKs by direct dephosphorylation. Here, we report that recombinant histidine (His)-AtPTP1 protein activity is directly inhibited by H2O2 and nitric oxide (NO) exogenous treatments. The effects of NO are exerted by S-nitrosation, i.e., the formation of a covalent bond between NO and a reduced cysteine residue. This post-translational modification targets the catalytic cysteine C265 and could protect the AtPTP1 protein from its irreversible oxidation by H2O2. This mechanism of protection could be a conserved mechanism in plant PTPases.
Highlights
Protein phosphatases and protein kinases are key enzymes that regulate many biological processes by protein dephosphorylation or phosphorylation, respectively
In regard to its key role in signaling, we investigated here whether Arabidopsis thaliana protein tyrosine phosphatase 1 (AtPTP1) could be modified by S-nitrosation as reported for PTP1B
We named the peptides generated after trypsin cleavage by their order in the protein sequence and by the number of the Cys contained in the peptide
Summary
Protein phosphatases and protein kinases are key enzymes that regulate many biological processes by protein dephosphorylation or phosphorylation, respectively. In Eukaryotes, protein phosphatases are classified in two major categories according to the amino acid target residue(s) of the dephosphorylation process: protein tyrosine (Tyr) phosphatases (PTPases; EC 3.1.3.48) and phosphoprotein serine/threonine (Ser/Thr) phosphatases (PPases). PTPases are themselves divided into two subgroups: tyrosine-specific protein tyrosine phosphatases (Tyr-specific PTPases), which include intracellular PTPases and receptor-like PTPases, and dual-specificity PTPases that constitute a particular subgroup of. Tyr phosphorylation and Tyr dephosphorylation have recently emerged as important mechanisms for transmembrane signaling in plants, in particular in immunity processes (Mühlenbeck et al, 2021)
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