The effect of PKA-phosphorylation on the structure of inhibitor-1 studied by NMR spectroscopy.
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.
Huang
Yi-Choang
YC
Institute of Biochemistry and Molecular Biology, Taipei Veterans General Hospital, Taipei 112, Taiwan, Republic of China.
Chen
Yi-Chen
YC
Tsay
Huey-Jen
HJ
Chyan
Chia-Lin
CL
Chen
Chun-Yu
CY
Huang
Hsien-Bin
HB
Lin
Ta-Hsien
TH
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*
D011506:Proteins; C073882:phosphoprotein phosphatase inhibitor 1; D017868:Cyclic AMP-Dependent Protein Kinases