I1PP2A-GST

Background: The Protein Phosphatase 2A (PP2A) inhibitor proteins, I1PP2A and I2PP2A/SET, were discovered in the laboratory of GloboZymes founder Dr. Zahi Damuni during his tenure as a faculty member at The Pennsylvania State University College of Medicine. These observations have been confirmed and extended in numerous laboratories around the world demonstrating further the significance of these proteins in various diseases including cancer and Alzheimers. Purified preparations of I1PP2A inhibit all forms of PP2A tested to date in a substrate-selective manner. Thus, the purified preparations inhibit PP2A potently (k_i ~ 0.1 nM) with Myelin Basic Protein (MBP) and Histone H1 but not with Casein as substrate. In contrast, purified preparations of I1PP2A stimulate PP1 activity in the presence of Mn2+ also in a substrate-selective manner. In cells, I1PP2A undergoes phosphorylation on serine and tyrosine residues. The function of the serine phosphorylation is uncertain. Tyrosine phsophorylation of I1PP2A occurs in response to the antiproliferative lectin Jacalin, and causes the dissociation of the I1PP2A PP2A complex resulting in the activation of the phosphatase.

References:  Li M, Makkinje A, Damuni Z. (1996) Biochemistry 35, 6998-7002; Vaesen, M. et al (1994) Biol Chem Hoppe Seyler 375, 113-126; Malek, S. N. et al (1990) J Biol Chem 265, 13400-13409; Li, M., Damuni, Z. (1998) Methods Mol Biol  93, 59-66; Katayose, Y. et al (2000) J Biol Chem 275, 9209-9214; Yu L-G et al (2004) J Biol Chem 279, 41377-41383