InterPro domain: IPR041754

PP7 is a plant phosphoprotein phosphatase that is highly expressed in a subset of stomata and thought to play an important role in sensory signaling. PP7 acts as a positive regulator of signaling downstream of cryptochrome blue light photoreceptors [ 1 ]. PP7 also controls amplification of phytochrome signaling, and interacts with nucleotidediphosphate kinase 2 (NDPK2), a positive regulator of phytochrome signalling. In addition, PP7 interacts with heat shock transcription factor HSF and up-regulates protective heat shock proteins [ 2 , 3 ]. PP7 may also play a role in salicylic acid-dependent defense signaling [ 4 ].

The PPP (phosphoprotein phosphatase) family, to which PP7 belongs, is one of two known protein phosphatase families specific for serine and threonine. The PPP family also includes: PP2A, PP2B (calcineurin), PP4, PP5, PP6, Bsu1, RdgC, PrpE, PrpA/PrpB, and ApA4 hydrolase. The PPP catalytic domain is defined by three conserved motifs (-GDXHG-, -GDXVDRG- and -GNHE-). The PPP enzyme family is ancient with members found in all eukaryotes, and in most bacterial and archeal genomes. Dephosphorylation of phosphoserines and phosphothreonines on target proteins plays a central role in the regulation of many cellular processes [ 5 , 6 ]. PPPs belong to the metallophosphatase (MPP) superfamily.

1. PP7 is a positive regulator of blue light signaling in Arabidopsis. Plant Cell 15, 1111-9
2. PPEF/PP7 protein Ser/Thr phosphatases. Cell. Mol. Life Sci. 66, 3103-10
3. PP7, a plant phosphatase representing a novel evolutionary branch of eukaryotic protein Ser/Thr phosphatases. Biochem. Mol. Biol. Int. 44, 703-15
4. The protein phosphatase 7 regulates phytochrome signaling in Arabidopsis. PLoS ONE 3, e2699
5. Recent progress on the structure of Ser/Thr protein phosphatases. Sci. China, C, Life Sci. 51, 487-94
6. Evolution of protein phosphatases in plants and animals. Biochem. J. 417, 401-9