1ed9
STRUCTURE OF E. COLI ALKALINE PHOSPHATASE WITHOUT THE INORGANIC PHOSPHATE AT 1.75A RESOLUTION
OverviewOverview
Here, X-ray crystallography has been used to investigate the proposed double in-line displacement mechanism of Escherichia coli alkaline phosphatase in which two of the three active-site metal ions have a direct role in catalysis. Two new X-ray crystal structures of the wild-type enzyme in the absence and presence of inorganic phosphate have been refined at 1.75 A to final working R-factors of 15.4% and 16.4%, respectively. In the refinement of both structures, residues in the active sites were treated anisotropically. The ellipsoids resulting from the partial anisotropic refinement show a clear route for the binding and release of substrate/product. In addition, a direct comparison of the refined structures with and without phosphate reveal a strong correlation between the occupancy of the third metal-binding site and the conformation of the Ser102 nucleophile. These findings clarify two important and unresolved aspects of the previously proposed catalytic mechanism, how Ser102 is activated for nucleophilic attack and why a magnesium ion in the third metal site is required for catalysis. Analysis of these results suggest that three metal-ion assisted catalysis is a more accurate description of the mechanism of the alkaline phosphatase reaction. A revised mechanism for the catalytic reaction of alkaline phosphatase is proposed on the basis of the two new X-ray crystal structures reported.
About this StructureAbout this Structure
1ED9 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
A revised mechanism for the alkaline phosphatase reaction involving three metal ions., Stec B, Holtz KM, Kantrowitz ER, J Mol Biol. 2000 Jun 23;299(5):1303-11. PMID:10873454 Page seeded by OCA on Fri May 2 14:57:28 2008