title: Structural analysis of a multifunctional, tandemly repeated inositol polyphosphatase.
abstract: Mitsuokella multacida expresses a unique inositol polyphosphatase (PhyAmm) that is composed of tandem repeats (TRs). Each repeat possesses a protein tyrosine phosphatase (PTP) active-site signature sequence and fold. Using a combination of structural, mutational, and kinetic studies, we show that the N-terminal (D1) and C-terminal (D2) active sites of the TR have diverged and possess significantly different specificities for inositol polyphosphate. Structural analysis and molecular docking calculations identify steric and electrostatic differences within the substrate binding pocket of each TR that may be involved in the altered substrate specificity. The implications of our results for the biological function of related PTP-like phytases are discussed. Finally, the structures and activities of PhyAmm and tandemly repeated receptor PTPs are compared and discussed. To our knowledge, this is the first example of an inositol phosphatase with tandem PTP domains possessing substrate specificity for different inositol phosphates.
authors.affiliation: Department of Chemistry and Biochemistry, University of Lethbridge, Alberta, Canada.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gruninger
authors.forename: L Brent
authors.initials: LB
authors.lastname: Selinger
authors.forename: Steven C
authors.initials: SC
authors.lastname: Mosimann
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray / Q000379:methods; D004252:DNA Mutational Analysis; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013379:Substrate Specificity; D020080:Tandem Repeat Sequences; D045854:Veillonellaceae / Q000201:enzymology* / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; C089504:polyphosphoinositide phosphatase; D010744:Phosphoric Monoester Hydrolases