Structural and biochemical characterization of inhibitor-1α

Hsien Bin Huang*, Yi Chen Chen, Ting Ting Lee, Yi Choang Huang, Hsin Tzu Liu, Chen Kuang Liu, Huey Jen Tsay, Ta Hsien Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Inhibitor-1α is one of the isoforms of human protein phosphatase inhibitor-1. It is a product of alternative splicing of inhibitor-1 gene and lacks 51 internal amino acids from residue 84 to 134 of inhibitor-1. Here we have characterized the structural and biochemical properties of inhibitor-1α. Structural analysis of recombinant inhibitor-1α by NMR spectroscopy revealed that inhibitor-1α adopts a predominantly random coil conformation. Excluding the region from residue 84 to 134 of inhibitor-1, the structural features of inhibitor-1 and inhibitor-1α are almost the same as each other. The IC50 value of inhibitor-1α in inhibition of Protein phosphatase-1 (PP1) is comparable to that of inhibitor-1, indicating that inhibitor-1α is a potent inhibitor of PP1 when Thr-35 is phosphorylated by PKA. For phosphorylation by PKA and dephosphorylation by protein phosphatase-1, -2A, and -2B, the measured kinetic parameters of inhibitor-1α are very close to those of inhibitor-1. Taken together, these results suggest that inhibitor-1α preserves the structure of inhibitor-1, the PP1 inhibitory activity and the functional specificities toward phosphorylation by PKA and dephosphorylation by protein phosphatase-1, -2A, and -2B.

Original languageEnglish
Pages (from-to)779-788
Number of pages10
JournalProteins: Structure, Function and Genetics
Issue number3
StatePublished - 15 Aug 2007


  • Dephosphorylation
  • Inhibitor-1
  • NMR
  • PKA
  • Phosphorylation
  • Protein phosphatase-1


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