1zic
Crystal Structure Analysis of the dienelactone hydrolase (C123S, R206A) mutant- 1.7 A
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OverviewOverview
The enzyme dienelactone hydrolase (DLH) has undergone directed evolution, to produce a series of mutant proteins that have enhanced activity towards, the non-physiological substrates alpha-naphthyl acetate and p-nitrophenyl, acetate. In terms of steady-state kinetics, the mutations caused a drop in, the K(m) for the hydrolysis reaction with these two substrates. For the, best mutant, there was a 5.6-fold increase in k(cat)/K(m) for the, hydrolysis of alpha-naphthyl acetate and a 3.6-fold increase was observed, for p-nitrophenyl acetate. For alpha-naphthyl acetate the pre-steady-state, kinetics revealed that the rate constant for the formation of the covalent, intermediate had increased. The mutations responsible for the rate, enhancements map to the active site. The structures of the starting and, mutated proteins revealed small changes in the protein owing to the, mutations, while the structures of the same proteins with an inhibitor, co-crystallized in the active site indicated that the mutations caused, significant changes in the way the mutated proteins recognized the, substrates. Within the active site of the mutant proteins, the inhibitor, was rotated by about 180 degrees with respect to the orientation found in, the starting enzyme. This rotation of the inhibitor caused the, displacement of a large section of a loop on one side of the active site., Residues that could stabilize the transition state for the reaction were, identified.
About this StructureAbout this Structure
1ZIC is a Single protein structure of sequence from Pseudomonas putida with SO4 and GOL as ligands. Active as Carboxymethylenebutenolidase, with EC number 3.1.1.45 Full crystallographic information is available from OCA.
ReferenceReference
Following directed evolution with crystallography: structural changes observed in changing the substrate specificity of dienelactone hydrolase., Kim HK, Liu JW, Carr PD, Ollis DL, Acta Crystallogr D Biol Crystallogr. 2005 Jul;61(Pt 7):920-31. Epub 2005, Jun 24. PMID:15983415
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