title: The structure of L-ribulose-5-phosphate 4-epimerase: an aldolase-like platform for epimerization.
abstract: The structure of L-ribulose-5-phosphate 4-epimerase from E. coli has been solved to 2.4 A resolution using X-ray diffraction data. The structure is homo-tetrameric and displays C(4) symmetry. Each subunit has a single domain comprised of a central beta-sheet flanked on either side by layers of alpha-helices. The active site is identified by the position of the catalytic zinc residue and is located at the interface between two adjacent subunits. A remarkable feature of the structure is that it shows a very close resemblance to that of L-fuculose-1-phosphate aldolase. This is consistent with the notion that both enzymes belong to a superfamily of epimerases/aldolases that catalyze carbon-carbon bond cleavage reactions via a metal-stabilized enolate intermediate. Detailed inspection of the epimerase structure, however, indicates that despite the close overall structural similarity to class II aldolases, the enzyme has evolved distinct active site features that promote its particular chemistry.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Luo
authors.forename: J
authors.initials: J
authors.lastname: Samuel
authors.forename: S C
authors.initials: SC
authors.lastname: Mosimann
authors.forename: J E
authors.initials: JE
authors.lastname: Lee
authors.forename: M E
authors.initials: ME
authors.lastname: Tanner
authors.forename: N C
authors.initials: NC
authors.lastname: Strynadka
mesh_terms: D000446:Aldehyde-Lyases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D002238:Carbohydrate Epimerases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D000446:Aldehyde-Lyases; C036027:L-fuculosephosphate aldolase; D002238:Carbohydrate Epimerases; C022554:L-ribulosephosphate 4-epimerase