title: The effect of PKA-phosphorylation on the structure of inhibitor-1 studied by NMR spectroscopy.
abstract: Inhibitor-1 is an acid- and heat-stable protein. It can be turned into a potent inhibitor of protein phosphatase-1 (PP1) after phosphorylation at Thr35 by c-AMP-dependent protein kinase (PKA). Although it has been known that pre-phosphorylation is essential for inhibition of PP1, the structure-function relationship of Thr(35)-phosphorylated inhibitor-1, such as whether or not PKA-phosphorylation pre-triggers conformational changes in inhibitor-1, remains unclear. In this study, we performed structural characterization of Thr(35)-phosphoroylated inhibitor-1 by using multi-dimensional heternuclear NMR spectroscopy. The result of structural comparison between Thr(35)-phosphoroylated and non-phosphorylated inhibitor-1 indicated that PKA-phosphorylation has no significant effect on the global conformation of free-state inhibitor-1. This finding may support the inference that regulation of the interactions between inhibitor-1 and PP1 through PKA-phosphorylation mainly depends on the phosphate group instead of phosphorylation-induced conformational change.
authors.affiliation: Institute of Biochemistry and Molecular Biology, Taipei Veterans General Hospital, Taipei 112, Taiwan, Republic of China.
authors.forename: Yi-Choang
authors.initials: YC
authors.lastname: Huang
authors.forename: Yi-Chen
authors.initials: YC
authors.lastname: Chen
authors.forename: Huey-Jen
authors.initials: HJ
authors.lastname: Tsay
authors.forename: Chia-Lin
authors.initials: CL
authors.lastname: Chyan
authors.forename: Chun-Yu
authors.initials: CY
authors.lastname: Chen
authors.forename: Hsien-Bin
authors.initials: HB
authors.lastname: Huang
authors.forename: Ta-Hsien
authors.initials: TH
authors.lastname: Lin
mesh_terms: D002942:Circular Dichroism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010766:Phosphorylation; D011506:Proteins / Q000737:chemistry*
chemical_list: D011506:Proteins; C073882:phosphoprotein phosphatase inhibitor 1; D017868:Cyclic AMP-Dependent Protein Kinases