2-Cys Peroxiredoxin glutathionylation is involved in chloroplast Fructose-1,6-Bisphosphatase activation

CAPORALETTI, D.; ARAN, M.; WOLOSIUK, R.A.

Rosario, Argentina.

Congreso; XLII SAIB ANNUAL MEETING; 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

2-Cys Peroxiredoxins (2-Cys Prx) are ubiquitous heme-free peroxidases that possess two conserved cysteines involved in the detoxification of reactive oxygen species and redox signalling. In particular, oxidized derivatives of the Cys in the Nterminal region are implicated in the peroxidase activity and cell redox regulation. We found that rapeseed 2-Cys Prx stimulates the activity of chloroplast fructose-1,6-bisphosphatase (CFBPase) through a mechanism different from the reductive activation. In order to analyze the action of cysteine chemical modifications on the activity of CFBPase, we prepared the reduced, the S-glutathionylated; the superoxidized (Cys53- SO3H) and the phosphorylated forms of rapeseed 2-Cys Prx and subsequently confirmed the derivatization by MALDI-TOF. Only 2-Cys Prx bearing a glutathione moiety exhibited the capacity to enhance CFBPase activity. Remarkably, the polypeptide was glutathionylated on both Cys53 and Cys175 when incubated at pH 8 but only in Cys175 when incubated at pH 8.5. Of these preparations, the former stimulated the activity of CFBPase. These results suggest that the incorporation of a glutathione moiety to Cys53 may be essential for the mechanism of CFBPase activation. Hence, our results provide insights about signalling via the S-glutathionylation of proteins, an alternative well-studied in mitochondria but yet unexplored in chloroplast.