2EB6

Crystal structure of HpcG complexed with Mg ion

Summary for 2EB6

• Entry DOI: 10.2210/pdb2eb6/pdb
• Related: 2EB4 2EB5
• Descriptor: 2-oxo-hept-3-ene-1,7-dioate hydratase, MAGNESIUM ION (3 entities in total)
• Functional Keywords: lyase, hydratase
• Biological source: Escherichia coli
• Total number of polymer chains: 5
• Total formula weight: 148875.67

Authors

Izumi, A.,Rea, D.,Adachi, T.,Unzai, S.,Park, S.Y.,Roper, D.I.,Tame, J.R.H. (deposition date: 2007-02-07, release date: 2007-07-17, Last modification date: 2023-10-25)

Primary citation

Izumi, A.,Rea, D.,Adachi, T.,Unzai, S.,Park, S.Y.,Roper, D.I.,Tame, J.R.H.
Structure and Mechanism of HpcG, a Hydratase in the Homoprotocatechuate Degradation Pathway of Escherichia coli
J.Mol.Biol., 370:899-911, 2007

PubMed Abstract: HpcG catalyses the hydration of a carbon-carbon double bond without the aid of any cofactor other than a simple divalent metal ion such as Mg(2+). Since the substrate has a nearby carbonyl group, it is believed that it first isomerises to form a pair of conjugated double bonds in the enol tautomer before Michael addition of water. Previous chemical studies of the reaction, and that of the related enzyme MhpD, have failed to provide a clear picture of the mechanism. The substrate itself is unstable, preventing co-crystallisation or soaking of crystals, but oxalate is a strong competitive inhibitor. We have solved the crystal structure of the protein in the apo form, and with magnesium and oxalate bound. Modelling substrate into the active site suggests the attacking water molecule is not part of the metal coordination shell, in contrast to a previous proposal. Our model suggests that geometrically strained cis isomer intermediates do not lie on the reaction pathway, and that separate groups are involved in the isomerisation and hydration steps.

PubMed: 17559873
DOI: 10.1016/j.jmb.2007.05.006

Experimental method

X-RAY DIFFRACTION (1.69 Å)