AUTHOR=Selles Benjamin , Dhalleine Tiphaine , Boutilliat Alexis , Rouhier Nicolas , Couturier Jérémy 

TITLE=A Redox-Sensitive Cysteine Is Required for PIN1At Function

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.735423

DOI=10.3389/fpls.2021.735423

ISSN=1664-462X

ABSTRACT=<p>Parvulins are ubiquitous peptidyl-prolyl isomerases (PPIases) required for protein folding and regulation. Among parvulin members, Arabidopsis PIN1At, human PIN1, and yeast ESS1 share a conserved cysteine residue but differ by the presence of an N-terminal WW domain, absent in PIN1At. In this study, we have explored whether the cysteine residue of Arabidopsis PIN1At is involved in catalysis and subject to oxidative modifications. From the functional complementation of yeast <italic>ess1</italic> mutant, we concluded that the cysteine at position 69 is mandatory for PIN1At function <italic>in vivo</italic>, unless being replaced by an Asp which is found in a few parvulin members. This result correlates with a decrease of the <italic>in vitro</italic> PPIase activity of non-functional PIN1At cysteinic variants. A decrease of PIN1At activity was observed upon H<sub>2</sub>O<sub>2</sub> treatment. The <italic>in vitro</italic> oxidation of cysteine 69, which has an acidic p<italic>K<sub>a</sub></italic> value of 4.9, leads to the formation of covalent dimers that are reduced by thioredoxins, or to sulfinic or sulfonic acid forms at higher H<sub>2</sub>O<sub>2</sub> excess. These investigations highlight the importance of the sole cysteine residue of PIN1At for activity. The reversible formation of an intermolecular disulfide bond might constitute a protective or regulatory mechanism under oxidizing conditions.</p>