Protein Phosphatase 4, Regulatory Subunit 1 (PPP4R1)

Protein phosphorylation on serine and threonine residues by protein kinases is responsible for the communication of many intracellular signals. Equally important is the dephosphorylation of proteins by ser/thr phosphatases; see, for example, PPP2R1B and PPP2CA.human PPP4R1 cDNA clone encoding a 933-amino acid protein. Sequence analysis identified 13 'heat' repeats that are similar to those in the regulatory component PP2A-A of PPP2R1B but are not contiguous. Mass spectrometry analysis indicated that PPP4R1 is a 105-kD protein, whereas SDS-PAGE analysis showed a doublet migrating at 120 to 125 kD. Immunoblot analysis revealed that PPP4R1 copurifies with PPP4C, suggesting that the PPP4 complex contains at least 1 catalytic and 1 regulatory subunit.