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Phosphorylation-Induced Conformational Switching Of Cpi-17 Produces A Potent Myosin Phosphatase Inhibitor, Masumi Eto, Toshio Kitazawa, Fumiko Matsuzawa, Sei-Ichi Aikawa, Jason A. Kirkbride, Noriyoshi Isozumi, Yumi Nishimura, David L. Brautigan, Shin-Ya Ohki
Phosphorylation-Induced Conformational Switching Of Cpi-17 Produces A Potent Myosin Phosphatase Inhibitor, Masumi Eto, Toshio Kitazawa, Fumiko Matsuzawa, Sei-Ichi Aikawa, Jason A. Kirkbride, Noriyoshi Isozumi, Yumi Nishimura, David L. Brautigan, Shin-Ya Ohki
Department of Molecular Physiology and Biophysics Faculty Papers
Phosphorylation of endogenous inhibitor proteins specific for type-1 Ser/Thr phosphatase (PP1) provides a mechanism for reciprocal coordination of kinase and phosphatase activities. Phosphorylation of Thr38 in the inhibitor protein CPI-17 transduces G-protein-mediated signaling into a > 1000-fold increase of inhibitory potency toward myosin phosphatase. We show here the solution NMR structure of phospho-T38-CPI-17 with r. m. s. d. of 0.36 ± 0.06 Å for the backbone secondary structure, which reveals how phosphorylation triggers a conformational change and exposes the PP1 inhibitory surface. This active conformation is stabilized by the formation of a hydrophobic core of intercalated side-chains, which is not formed …