1fq0
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(New page: 200px<br /><applet load="1fq0" size="450" color="white" frame="true" align="right" spinBox="true" caption="1fq0, resolution 2.10Å" /> '''KDPG ALDOLASE FROM E...)
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Revision as of 13:01, 20 November 2007
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KDPG ALDOLASE FROM ESCHERICHIA COLI
Overview
BACKGROUND: Aldolases are carbon bond-forming enzymes that have long been, identified as useful tools for the organic chemist. However, their utility, is limited in part by their narrow substrate utilization. Site-directed, mutagenesis of various enzymes to alter their specificity has been, performed for many years, typically without the desired effect. More, recently directed evolution has been employed to engineer new activities, onto existing scaffoldings. This approach allows random mutation of the, gene and then selects for fitness to purpose those proteins with the, desired activity. To date such approaches have furnished novel activities, through multiple mutations of residues involved in recognition; in no, instance has a key catalytic residue been altered while activity is, retained. RESULTS: We report a double mutant of E. coli, 2-keto-3-deoxy-6-phosphogluconate aldolase with reduced but measurable, enzyme activity and a synthetically useful substrate profile. The mutant, was identified from directed-evolution experiments. Modification of, substrate specificity is achieved by altering the position of the active, site lysine from one beta strand to a neighboring strand rather than by, modification of the substrate recognition site. The new enzyme is, different to all other existing aldolases with respect to the location of, its active site to secondary structure. The new enzyme still displays, enantiofacial discrimination during aldol addition. We have determined the, crystal structure of the wild-type enzyme (by multiple wavelength methods), to 2.17 A and the double mutant enzyme to 2.7 A resolution. CONCLUSIONS:, These results suggest that the scope of directed evolution is, substantially larger than previously envisioned in that it is possible to, perturb the active site residues themselves as well as surrounding loops, to alter specificity. The structure of the double mutant shows how, catalytic competency is maintained despite spatial reorganization of the, active site with respect to substrate.
About this Structure
1FQ0 is a Single protein structure of sequence from Escherichia coli with CIT as ligand. Active as 2-dehydro-3-deoxy-phosphogluconate aldolase, with EC number 4.1.2.14 Full crystallographic information is available from OCA.
Reference
Directed evolution of a new catalytic site in 2-keto-3-deoxy-6-phosphogluconate aldolase from Escherichia coli., Wymer N, Buchanan LV, Henderson D, Mehta N, Botting CH, Pocivavsek L, Fierke CA, Toone EJ, Naismith JH, Structure. 2001 Jan 10;9(1):1-9. PMID:11342129
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