Structural and biochemical characterization of inhibitor-1alpha.
Inhibitor-1alpha 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-1alpha. Structural analysis of recombinant inhibitor-1alpha by NMR spectroscopy revealed that inhibitor-1alpha 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-1alpha are almost the same as each other. The IC(50) value of inhibitor-1alpha in inhibition of Protein phosphatase-1 (PP1) is comparable to that of inhibitor-1, indicating that inhibitor-1alpha 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-1alpha are very close to those of inhibitor-1. Taken together, these results suggest that inhibitor-1alpha 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.
Huang
Hsien-Bin
HB
Institute of Molecular Biology, National Chung Cheng University, Chia-Yi 621, Taiwan, Republic of China.
Chen
Yi-Chen
YC
Lee
Ting-Ting
TT
Huang
Yi-Choang
YC
Liu
Hsin-Tzu
HT
Liu
Chen-Kuang
CK
Tsay
Huey-Jen
HJ
Lin
Ta-Hsien
TH
D000818:Animals; D020134:Catalytic Domain; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D019906:Nuclear Magnetic Resonance, Biomolecular; D009687:Nuclear Proteins; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D011487:Protein Conformation; D054645:Protein Phosphatase 1; D016601:RNA-Binding Proteins; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
C087425:ANP32A protein, human; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1