Substrate binding in protein-tyrosine phosphatase-like inositol polyphosphatases.
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Gruninger RJ, Dobing S, Smith AD, Bruder LM, Selinger LB, Wieden HJ, Mosimann SC
Substrate binding in protein-tyrosine phosphatase-like inositol polyphosphatases.
J Biol Chem. 2012 Mar 23;287(13):9722-30. doi: 10.1074/jbc.M111.309872. Epub 2011 Dec 2.
- PubMed ID
- 22139834 [ View in PubMed]
- Abstract
Protein-tyrosine phosphatase-like inositol polyphosphatases are microbial enzymes that catalyze the stepwise removal of one or more phosphates from highly phosphorylated myo-inositols via a relatively ordered pathway. To understand the substrate specificity and kinetic mechanism of these enzymes we have determined high resolution, single crystal, x-ray crystallographic structures of inactive Selenomonas ruminantium PhyA in complex with myo-inositol hexa- and pentakisphosphate. These structures provide the first glimpse of a myo-inositol polyphosphatase-ligand complex consistent with its known specificity and reveal novel features of the kinetic mechanism. To complement the structural studies, fluorescent binding assays have been developed and demonstrate that the K(d) for this enzyme is several orders of magnitude lower than the K(m). Together with rapid kinetics data, these results suggest that the protein tyrosine phosphatase-like inositol polyphosphatases have a two-step, substrate-binding mechanism that facilitates catalysis.