title: Secondary structure of Escherichia coli glucosamine-6-phosphate deaminase from amino acid sequence and circular dichroism spectroscopy.
abstract: The secondary structure of the purified glucosamine-6-phosphate deaminase from Escherichia coli K12 was investigated by both circular dichroism (CD) spectroscopy and empirical prediction methods. The enzyme was obtained by allosteric-site affinity chromatography from an overproducing strain bearing a pUC18 plasmid carrying the structural gene for the enzyme. From CD analysis, 34% of alpha-helix, 9% of parallel beta-sheet, 11% of antiparallel beta-sheet, 15% turns and 35% of non-repetitive structures, were estimated. A joint prediction scheme, combining six prediction methods with defined rules using several physicochemical indices, gave the following values: alpha-helix, 37%; beta-sheet, 22%; turns, 18% and coil, 23%. The structure predicted showed also a considerable degree of alternacy of alpha and beta structures; 64% of helices are amphipathic and 90% of beta-sheets are hydrophobic. Overall, the data suggest that deaminase has as dominant motif, an alpha/beta structure.
authors.affiliation: Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City.
authors.forename: M M
authors.initials: MM
authors.lastname: Altamirano
authors.forename: J A
authors.initials: JA
authors.lastname: Plumbridge
authors.forename: A
authors.initials: A
authors.lastname: Hernández-Arana
authors.forename: M
authors.initials: M
authors.lastname: Calcagno
mesh_terms: D019747:Aldose-Ketose Isomerases; D000595:Amino Acid Sequence; D002238:Carbohydrate Epimerases / Q000737:chemistry* / Q000302:isolation & purification; D002942:Circular Dichroism; D004926:Escherichia coli / Q000201:enzymology*; D008961:Models, Structural; D011487:Protein Conformation
chemical_list: C020582:glucosamine-6-phosphate isomerase; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases