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The plant thimet oligopeptidases TOP1 and TOP2 have divergent redox sensitivities and substrate cleavage specificity

ABSTRACT: Physiological and pathogen-induced oscillations in the plant cells' redox environment trigger response mechanisms that involve redox-sensitive cysteines and consequent changes in proteins' biochemical and functional characteristics. Arabidopsis thimet oligopeptidases (TOPs) TOP1 and TOP2 are components of the immune signaling and oxidative stress response. Here, TOP1 and TOP2 were evaluated comparatively to understand their role as redox sensors. We show that TOPs catalytic activity is augmented in plants undergoing an immune response and in mutant lines with altered expression of the chloroplastic NTRC impaired in the chloroplast thiol-disulfide regulatory system; ntrc was unable to mount a systemic immune response. Oxidation promoted TOP1 self-interaction to dimers and oligomers; Cys-to-Ala mutagenesis of multiple Cys residues inhibited TOP1 oxidative self-interaction. In contrast, TOP1 lacking the signal peptide (ΔSPTOP1) and TOP2 were detected solely as monomers. Treatment with oxidized glutathione increased the catalytic activities of TOPs; Ala substitution of the unique Cys405 of TOP2 abolished its oxidative activation. The immune regulator ROC1 was identified as a candidate TOPs substrate. TOPs cleaved a ROC1 peptide (ROC1p) at similar and unique cleavage sites; ROC1p concentration helped determine TOPs cleavage specificity. We propose that TOP1 and TOP2 form a proteolysis couple with divergent redox-sensing mechanisms and specificity.

INSTRUMENT(S): Q Exactive HF-X

ORGANISM(S): Escherichia Coli

SUBMITTER: Leslie Hicks

LAB HEAD: Leslie Hicks

PROVIDER: PXD024059 | Pride | 2021-04-19

REPOSITORIES: Pride

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