title: Structure-based annotation of a novel sugar isomerase from the pathogenic E. coli O157:H7.
abstract: Prokaryotes can use a variety of sugars as carbon sources in order to provide a selective survival advantage. The gene z5688 found in the pathogenic Escherichia coli O157:H7 encodes a "hypothetical" protein of unknown function. Sequence analysis identified the gene product as a putative member of the cupin superfamily of proteins, but no other functional information was known. We have determined the crystal structure of the Z5688 protein at 1.6 A resolution and identified the protein as a novel E. coli sugar isomerase (EcSI) through overall fold analysis and secondary-structure matching. Extensive substrate screening revealed that EcSI is capable of acting on d-lyxose and d-mannose. The complex structure of EcSI with fructose allowed the identification of key active-site residues, and mutagenesis confirmed their importance. The structure of EcSI also suggested a novel mechanism for substrate binding and product release in a cupin sugar isomerase. Supplementation of a nonpathogenic E. coli strain with EcSI enabled cell growth on the rare pentose d-lyxose.
authors.affiliation: Department of Biochemistry, Queen's University, Kingston, Ontario, Canada K7L3N6.
authors.forename: Laura M
authors.initials: LM
authors.lastname: van Staalduinen
authors.forename: Chang-Su
authors.initials: CS
authors.lastname: Park
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Yeom
authors.forename: Melanie A
authors.initials: MA
authors.lastname: Adams-Cioaba
authors.forename: Deok-Kun
authors.initials: DK
authors.lastname: Oh
authors.forename: Zongchao
authors.initials: Z
authors.lastname: Jia
mesh_terms: D000595:Amino Acid Sequence; D002412:Cations; D018360:Crystallography, X-Ray; D019281:Dimerization; D019453:Escherichia coli O157 / Q000201:enzymology* / Q000254:growth & development; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D007535:Isomerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D002412:Cations; D007535:Isomerases