title: Atomic structure of dual-specificity phosphatase 26, a novel p53 phosphatase.
abstract: Regulation of p53 phosphorylation is critical to control its stability and biological activity. Dual-specificity phosphatase 26 (DUSP26) is a brain phosphatase highly overexpressed in neuroblastoma, which has been implicated in dephosphorylating phospho-Ser20 and phospho-Ser37 in the p53 transactivation domain. In this paper, we report the 1.68 Å crystal structure of a catalytically inactive mutant (Cys152Ser) of DUSP26 lacking the first 60 N-terminal residues (ΔN60-C/S-DUSP26). This structure reveals the architecture of a dual-specificity phosphatase domain related in structure to Vaccinia virus VH1. DUSP26 adopts a closed conformation of the protein tyrosine phosphatase (PTP)-binding loop, which results in an unusually shallow active site pocket and buried catalytic cysteine. A water molecule trapped inside the PTP-binding loop makes close contacts both with main chain and with side chain atoms. The hydrodynamic radius (R(H)) of ΔN60-C/S-DUSP26 measured from velocity sedimentation analysis (R(H) ∼ 22.7 Å) and gel filtration chromatography (R(H) ∼ 21.0 Å) is consistent with an ∼18 kDa globular monomeric protein. Instead in crystal, ΔN60-C/S-DUSP26 is more elongated (R(H) ∼ 37.9 Å), likely because of the extended conformation of C-terminal helix α9, which swings away from the phosphatase core to generate a highly basic surface. As in the case of phosphatase MKP-4, we propose that a substrate-induced conformational change, possibly involving rearrangement of helix α9 with respect to the phosphatase core, allows DUSP26 to adopt a catalytically active conformation. The structural characterization of DUSP26 presented in this paper provides the first atomic insight into this disease-associated phosphatase.
authors.affiliation: Department of Biochemistry and Molecular Biology,  Thomas Jefferson University , 233 South 10th Street, Philadelphia, Pennsylvania 19107, United States.
authors.forename: Ravi Kumar
authors.initials: RK
authors.lastname: Lokareddy
authors.forename: Anshul
authors.initials: A
authors.lastname: Bhardwaj
authors.forename: Gino
authors.initials: G
authors.lastname: Cingolani
mesh_terms: D020134:Catalytic Domain; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D054637:Dual-Specificity Phosphatases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D054639:Mitogen-Activated Protein Kinase Phosphatases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D008958:Models, Molecular; D009447:Neuroblastoma / Q000201:enzymology; D011487:Protein Conformation; D055503:Protein Multimerization; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D014616:Vaccinia virus / Q000737:chemistry / Q000201:enzymology
chemical_list: D016159:Tumor Suppressor Protein p53; D054639:Mitogen-Activated Protein Kinase Phosphatases; C500883:DUSP26 protein, human; D054637:Dual-Specificity Phosphatases