The Backbone Resonance Assignments of Inhibitor 1 – a Protein  Inhibitor of Protein Phosphatase-1


Tzu-Chun Tang1, Hsin-Tzu Liu2, Hsien-bin Huang3, Yi-Chen Chen4, Chia-Lin Chyan1, Ta-Hsien Lin5

1Department of Chemistry, National Dong Hwa University, Hualien, Taiwan 974, ROC, 2Department of Research, Buddhist Chi Tzu General Hospital, 3Department of Biochemistry, National Chung Cheng University, Chia-Yi, Taiwan 621, ROC, 4Department of Medical Technology, Tzu-Chi University, Hualien, Taiwan 974, ROC, 5Department of Biochemistry, National Yang-Ming University, Taipei, Taiwan 112, ROC


Protein phosphatase-1 (PP1) is a major protein serine/threonine phosphatase in eukaryotic cells.  PP1 can regulate diverse cellular processes such as cell cycle, protein synthesis, transcription, neuronal signaling, etc.  The function of PP1 is regulated by the binding of heat-stable protein inhibitors such as inhibitor-1, -2, and DARPP-32.    Inhibitor-1 shares high sequence homology to DARPP-32, but no sequence homology to inhibitor-2.  The phophorylation at Thr-35 by cAMP-dependent protein kinase is essential to convert inhibitor-1 to a potent inhibitor of PP1.  To understand the structural basis of inhibitor-1 is important, when we study the PP1-regulation by their inhibitors.  Here, we are presenting the data on the unphosphorylated inhibitor-1 using NMR techniques.  A series of triple resonance NMR experiments including HNCA, HNCACO, HNCO, HNCACO, CBCANH, CBCACONH, HBHANH and HBHACONH were performed.  Backbone 1H, 15N, and 13C resonances of inhibitor-1 were assigned.  The unphosphorylated inhibitor-1 was found to be highly unstructured.