Structure of PP1 catalytic motif and the glc7-E101Q mutant. (A) PP1 protein phosphatases have highly conserved catalytic domains, consisting of residues acting as an acidic catalyst for phosphotransfer (CD1 and CD2) from the substrate and a phospho acceptor hisidine residue (CD3). Residues in the catalytic pocket are highly conserved between human (PP1), yeast PPP-type PPases (Glc7 and others) and the bacterial PPase, λ-PPASE. (B) Left panel: The Glc7 catalytic pocket (pink) was modeled using the tertiary structure of human PP1C-γ (PDB Model 1jk7A; blue). Right panels: The E101Q mutation is predicted to inhibit the binding of a metal cation required to accelerate phospho-transfer to H124, but to not alter the shape/size of the catalytic pocket relative to wild type Glc7.