title: A third metal is required for catalytic activity of the signal-transducing protein phosphatase M tPphA.
abstract: Protein phosphatase M (PPM) regulates key signaling pathways in prokaryotes and eukaryotes. Novel structures of bacterial PPM members revealed three divalent metal ions in their catalytic centers. The function of metal 3 (M3) remained unclear. To reveal its function, we created variants of tPphA from Thermosynechococcus elongatus in all metal-coordinating residues, and multiple variants were created for the M3 coordinating Asp-119 residue. The structures of variants D119A and D193A were resolved, showing loss of M3 binding but unaffected binding of M1 and M2 in the catalytic center of D119A, with the nucleophilic water molecule in the correct place. The catalytic activity of this variant was highly impaired. This and further structure-function analyses showed that M3 is required for catalysis by providing a water molecule as a proton donor during catalysis. Mutation of the homologue Asp residue in human PP2Cα also caused loss of function, suggesting a general requirement of M3 in PPM-catalyzed reactions.
authors.affiliation: Interfaculty Institute of Microbiology and Infection Medicine, Department of Organismic Interactions, University of Tübingen, Auf der Morgenstelle 28, D-72076 Tübingen, Germany.
authors.forename: Jiyong
authors.initials: J
authors.lastname: Su
authors.forename: Christine
authors.initials: C
authors.lastname: Schlicker
authors.forename: Karl
authors.initials: K
authors.lastname: Forchhammer
mesh_terms: D020134:Catalytic Domain; D000458:Cyanobacteria / Q000201:enzymology*; D006801:Humans; D008670:Metals / Q000737:chemistry* / Q000378:metabolism; D020125:Mutation, Missense; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D040681:Structural Homology, Protein; D013329:Structure-Activity Relationship
chemical_list: D008670:Metals; D010749:Phosphoprotein Phosphatases