Activity of AtPTP1, an Arabidopsis Protein Tyrosine Phosphatase, Is Regulated by Redox Status of the Non-Catalytic Cysteine Residue

Abstract

Mammalian protein tyrosine phosphatase (PTPase) is easily inactivated by oxidative modification of the catalytic cysteine residue. And plant PTPase is postulated to be regulated in a similar manner. However, we report that the activity of Arabidopsis PTPase (AtPTP1) is regulated by redox status of the non-catalytic cysteine residue. Wild type AtPTP1 was inactivated by oxidized glutathione (GSSG) or H₂O₂ in a dose-dependent manner. A mutant AtPTP1 where C175 was substituted for serine (C175S) showed more resistance to GSSG and H₂O₂, suggesting that AtPTP1 is regulated by redox status of the non-catalytic C175 rather than catalytic C265. Considering plants expressing the C175S mutant AtPTP1 showed stronger phenotype than those expressing wild-type AtPTP1, C175 is likely to be redox-regulated in vivo.