I-1; Inhibitor-1

Source: Recombinant human produced in E. coli

Purity: > 95% by SDS-PAGE, apparent Mr ~ 27-kDa

Supplied: 1 μg in 50 μl of 50 mM Tis-HCl pH 7.0 buffer containing 0.1 mM phenylmethanesulfonyl fluoride, 14 mM β-mercaptoethanol and 10% glycerol. Maintain in aliquots at -70°C. Avoid repeated freeze thaw cycles.

Suitable for identifying protein kinases and protein phosphatases which act on the highly purified preparations of the inhibitor protein and for measuring the effect on its activity with Type-1 protein serine/ threonine phosphatase preparations.

Synonyms: I1; Inhibitor 1

Background: Inhibitor-1 is a 171 amino acid protein with an average molecular weight of 18.9 kDa. It is a specific inhibitor of Type-1 protein serine/threonine phosphatases (PP1, GLO133-001). The IC50 for inhibition of PP1 is ~ 1 to 2 nm. The selectivity and potency of inhibitor-1 are conferred by its N-terminal sequence KIQF and its activation by phosphorylation at Thr35 catalyzed by protein kinase A. Dephosphorylation and inactivation can be carried out in the presence of Ca2+ by PP2B (Calcineurin, GLO134-001).


  1. Connor, J. H. et al (1998) "Inhibitor-1 interaction domain that mediates the inhibition of protein phosphatase-1" J. Biol. Chem. 273, 27716-27724
  2. Connor, J. H. et al (1999) "Importance of the beta12-beta13 loop in protein phosphatase-1 catalytic subunit for inhibition by toxins and mammalian protein inhibitors" J. Biol. Chem 274, 22366-22372
  3. Endo, S. et al (1996) “Multiple structural elements define the specificity of recombinant human inhibitor-1 as a protein phosphatase-1 inhibitor” Biochemistry 35, 5220-5228
  4. Bibb, J. A. et al (2001) “Phosphorylation of protein phosphatase inhibitor-1 by Cdk5" J. Biol. Chem. 276, 14490-14497

Related ProductsPP1C ♦  PP2B

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