title: Distinctive solution conformation of phosphatase inhibitor CPI-17 substituted with aspartate at the phosphorylation-site threonine residue.
abstract: We present solution NMR structures for wild-type and mutated forms of CPI-17, a phosphoinhibitor for protein phosphatase 1. Phosphorylation of Thr38 of CPI-17 produces a >1000-fold increase in inhibitory potency for myosin phosphatase. We compared the 1H-15N heteronuclear single quantum coherence spectroscopy (HSQC) chemical shifts of wild-type CPI-17, partially phosphorylated CPI-17 and CPI-17 with Thr38 replaced with Asp to introduce a negative charge. There was a switch in the protein conformation due to either Asp substitution or phosphorylation, so we determined the solution NMR structure of the CPI-17 T38D mutant as a model for the active (phospho-) conformation. The structures reveal a molecular switch in conformation that involves the rotation of two of the four helices in the four helix bundle. Despite this conformational switch, there was little increase in the inhibitory potency with T38D. We propose that for this inhibitor, a negative charge at residue 38 is sufficient to trigger an active conformation, but a phosphoryl group is required for full inhibitory potency against protein phosphatase-1.
authors.affiliation: CREST and Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Shin ya
authors.initials: Sy
authors.lastname: Ohki
authors.forename: Masumi
authors.initials: M
authors.lastname: Eto
authors.forename: Masato
authors.initials: M
authors.lastname: Shimizu
authors.forename: Rei
authors.initials: R
authors.lastname: Takada
authors.forename: David L
authors.initials: DL
authors.lastname: Brautigan
authors.forename: Masatsune
authors.initials: M
authors.lastname: Kainosho
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry*; D001665:Binding Sites; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D020128:Inhibitory Concentration 50; D008958:Models, Molecular; D009124:Muscle Proteins / Q000737:chemistry* / Q000378:metabolism; D043263:Myosin-Light-Chain Phosphatase; D019906:Nuclear Magnetic Resonance, Biomolecular; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D011487:Protein Conformation; D054645:Protein Phosphatase 1; D012996:Solutions; D013329:Structure-Activity Relationship; D013552:Swine; D013912:Threonine / Q000737:chemistry*
chemical_list: D004791:Enzyme Inhibitors; D009124:Muscle Proteins; D010750:Phosphoproteins; D012996:Solutions; D013912:Threonine; D001224:Aspartic Acid; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D043263:Myosin-Light-Chain Phosphatase