FAST REDOX RESPONSE OF IRON-SULFUR GLUTAREDOXIN GRXS17 ACTIVATES ITS HOLDASE ACTIVITY AND PROTECTS PLANTS FROM HEAT STRESS

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Martins, Laura | Knuesting, Johannes | Bariat, Laetitia | Freibert, Sven A | Marchand, Christophe H | Young, David | Lill, Roland | Messens, Joris | Scheibe, Renate | Riondet, Christophe | Reichheld, Jean-Philippe

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International audience. Arabidopsis GRXS17 is an iron-sulfur clusters (ISC) glutaredoxin that consists of an N-terminal TRX-domain and three CGFS-ac ve site mo f-containing GRX-domains, coordina ng three ISC in a glutathione (GSH)-dependent manner. As an ISC-charged holoenzyme, GRXS17 is likely involved in the matura on process of ISC-containing proteins. In addi on of its role in cluster biogenesis, we showed here that GRXS17 is a foldase with redoxdependent holdase ac vity. Oxida ve stress in combina on with heat stress induces loss of the ISC followed by sulfenyla on of ac ve site cysteines and subsequent forma on of disulfide bonds between conserved cysteines in the corresponding N-terminal TRX domains. This oxida on leads to the ac va on of the holdase ac vity, and shi s GRXS17 from a low-MW form to a high-MW complex. Furthermore, we showed that GRXS17 changes its client proteins under heat stress, and protects them from aggrega on. All in all, we reveal the mechanism of an ISC-dependent ac vity shi , turning the holoenzyme GRXS17 into a holdase that prevents damage under heat stress.

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