title: Crystal structure of the catalytic subunit of human protein phosphatase 1 and its complex with tungstate.
abstract: Protein phosphatase 1 (PP1) is a serine/threonine protein phosphatase that is essential in regulating diverse cellular processes. Here we report the crystal structure of the catalytic subunit of human PP1 gamma 1 and its complex with tungstate at 2.5 A resolution. The anomalous scattering from tungstate was used in a multiple wavelength anomalous dispersion experiment to derive crystallographic phase information. The protein adopts a single domain with a novel fold, distinct from that of the protein tyrosine phosphatases. A di-nuclear ion centre consisting of Mn2+ and Fe2+ is situated at the catalytic site that binds the phosphate moiety of the substrate. Proton-induced X-ray emission spectroscopy was used to identify the nature of the ions bound to the enzyme. The structural data indicate that dephosphorylation is catalysed in a single step by a metal-activated water molecule. This contrasts with other phosphatases, including protein tyrosine phosphatases, acid and alkaline phosphatases which form phosphoryl-enzyme intermediates. The structure of PP1 provides insight into the molecular mechanism for substrate recognition, enzyme regulation and inhibition of this enzyme by toxins and tumour promoters and a basis for understanding the expanding family of related phosphatases which include PP2A and PP2B (calcineurin).
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D006801:Humans; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000378:metabolism; D054645:Protein Phosphatase 1; D013052:Spectrometry, X-Ray Emission; D013379:Substrate Specificity; D017973:Tungsten Compounds / Q000737:chemistry* / Q000378:metabolism
chemical_list: D017973:Tungsten Compounds; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C045951:tungstate