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The three-dimensional structure of mannosyl-3-phosphoglycerate phosphatase from Thermus thermophilus HB27: a new member of the Haloalkanoic Acid Dehalogenase Superfamily

DOI: 10.1021/bi201171h DOI Help
PMID: 21961705 PMID Help

Authors: Susana Goncalves (Instituto Tecnologia Quimica e Biologica) , Ana Esteves (Universidade Nova de Lisboa) , Helena Santos (Universidade Nova de Lisboa) , Nuno Borges (Universidade Nova de Lisboa) , Pedro Matias (Institudo Tecnologia Quimica e Biologica)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemistry

State: Published (Approved)
Published: September 2011

Abstract: Mannosyl-3-phosphoglycerate phosphatase (MpgP) is a key mediator in the physiological response to thermal and osmotic stresses, catalyzing the hydrolysis of mannosyl-3-phosphoglycerate (MPG) to the final product, ?-mannosylglycerate. MpgP is a metal-dependent haloalcanoic acid dehalogenase-like (HAD-like) phosphatase, preserving the catalytic motifs I–IV of the HAD core domain, and classified as a Cof-type MPGP (HAD-IIB-MPGP family; SCOP [117505]) on the basis of its C2B cap insertion module. Herein, the crystallographic structures of Thermus thermophilus HB27 MpgP in its apo form and in complex with substrates, substrate analogues, and inhibitors are reported. Two distinct enzyme conformations, open and closed, are catalytically relevant. Apo-MpgP is primarily found in the open state, while holo-MpgP, in complex with the reaction products, is found in the closed state. Enzyme activation entails a structural rearrangement of motifs I and IV with concomitant binding of the cocatalytic Mg2+ ion. The closure motion of the C2B domain is subsequently triggered by the anchoring of the phosphoryl group to the cocatalytic metal center, and by Arg167 fixing the mannosyl moiety inside the catalytic pocket. The results led to the proposal that in T. thermophilus HB27 MpgP the phosphoryl transfer employs a concerted DNSN mechanism with assistance of proton transfer from the general acid Asp8, forming a short-lived PO3– intermediate that is attacked by a nucleophilic water molecule. These results provide new insights into a possible continuum of phosphoryl transfer mechanisms, ranging between those purely associative and dissociative, as well as a picture of the main mechanistic aspects of phosphoryl monoester transfer catalysis, common to other members of the HAD superfamily.

Journal Keywords: Catalysis; Crystallography; X-Ray; Glyceric; Hydrolases; Mannose; Models; Molecular; Multigene; Phosphotransferases; Protein; Thermus thermophilus

Subject Areas: Biology and Bio-materials

Instruments: I02-Macromolecular Crystallography , I03-Macromolecular Crystallography , I04-Macromolecular Crystallography