R. Gupta et al., Identification of a dual-specificity protein phosphatase that inactivates a MAP kinase from Arabidopsis, PLANT J, 16(5), 1998, pp. 581-589
Mitogen-activated protein kinases (MAPKs) play a key role in plant response
s to stress and pathogens. Activation and inactivation of MAPKs involve pho
sphorylation and dephosphorylation on both threonine and tyrosine residues
in the kinase domain. Here we report the identification of an Arabidopsis g
ene encoding a dual-specificity protein phosphatase capable of hydrolysing
both phosphoserine/threonine and phosphotyrosine in protein substrates. Thi
s enzyme, designated AtDsPTP1 (Arabidopsis thaliana dual-specificity protei
n tyrosine phosphatase), dephosphorylated and inactivated AtlWPK4, a MARK m
ember from the same plant. Replacement of a highly conserved cysteine by se
rine abolished phosphatase activity of AtDsPTP1, indicating a conserved cat
alytic mechanism of dual-specificity protein phosphatases from all eukaryot
es.