PP7, a recently identified protein Ser/Thr phosphatase of the PPP family distantly related to phosphatases PP5/PPT and PPEF/rdgC, was purified from cauliflower extracts to apparent homogeneity. Purified cauliflower PP7 and recombinant PP7 expressed in
Escherichia coli exhibit light absorption in the visible range with a maximum at
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430 nm. Under nonreducing conditions, native PP7 exists as a mixture of monomer with an intramolecular disulfide bridge, disulfide-linked homodimer, and possibly disulfide-linked complexes with potential partner proteins. The activity of recombinant
Arabidopsis thaliana PP7 is reversibly regulated by redox agents. The results demonstrate the existence of PP7 protein
in planta and suggest a possibility of redox regulation of this protein phosphatase.