2isw
Structure of Giardia fructose-1,6-biphosphate aldolase in complex with phosphoglycolohydroxamate
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OverviewOverview
Class I and class II fructose-1,6-bisphosphate aldolases (FBPA), glycolytic pathway enzymes, exhibit no amino acid sequence homology and, utilize two different catalytic mechanisms. The mammalian class I FBPA, employs a Schiff base mechanism, whereas the human parasitic protozoan, Giardia lamblia class II FBPA is a zinc-dependent enzyme. In this study, we have explored the potential exploitation of the Giardia FBPA as a drug, target. First, synthesis of FBPA was demonstrated in Giardia trophozoites, by using an antibody-based fluorescence assay. Second, inhibition of FBPA, gene transcription in Giardia trophozoites suggested that the enzyme is, necessary for the survival of the organism under optimal laboratory growth, conditions. Third, two crystal structures of FBPA in complex with the, transition state analog phosphoglycolohydroxamate (PGH) show that the, enzyme is homodimeric and that its active site contains a zinc ion. In one, crystal form, each subunit contains PGH, which is coordinated to the zinc, ion through the hydroxamic acid hydroxyl and carbonyl oxygen atoms. The, second crystal form contains PGH only in one subunit and the active site, of the second subunit is unoccupied. Inspection of the two states of the, enzyme revealed that it undergoes a conformational transition upon ligand, binding. The enzyme cleaves d-fructose-1,6-bisphosphate but not, d-tagatose-1,6-bisphosphate, which is a tight binding competitive, inhibitor. The essential role of the active site residue Asp-83 in, catalysis was demonstrated by amino acid replacement. Determinants of, catalysis and substrate recognition, derived from comparison of the G., lamblia FBPA structure with Escherichia coli FBPA and with a closely, related enzyme, E. coli tagatose-1,6-bisphosphate aldolase (TBPA), are, described.
About this StructureAbout this Structure
2ISW is a Single protein structure of sequence from Giardia intestinalis with and as ligands. Active as Fructose-bisphosphate aldolase, with EC number 4.1.2.13 Full crystallographic information is available from OCA.
ReferenceReference
Characterization, kinetics, and crystal structures of fructose-1,6-bisphosphate aldolase from the human parasite, Giardia lamblia., Galkin A, Kulakova L, Melamud E, Li L, Wu C, Mariano P, Dunaway-Mariano D, Nash TE, Herzberg O, J Biol Chem. 2007 Feb 16;282(7):4859-67. Epub 2006 Dec 13. PMID:17166851
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