title: Three-dimensional structure of the bifunctional enzyme N-(5'-phosphoribosyl)anthranilate isomerase-indole-3-glycerol-phosphate synthase from Escherichia coli.
abstract: N-(5'-Phosphoribosyl)anthranilate isomerase-indole-3-glycerol-phosphate synthase from Escherichia coli is a monomeric bifunctional enzyme of Mr 49,500 that catalyzes two sequential reactions in the biosynthesis of tryptophan. The three-dimensional structure of the enzyme has been determined at 2.8-A resolution by x-ray crystallography. The two catalytic activities reside on distinct functional domains of similar folding, that of an eightfold parallel beta-barrel with alpha-helices on the outside connecting the beta-strands. Both active sites were located with an iodinated substrate analogue and found to be in depressions on the surface of the domains created by the outward-curving loops between the carboxyl termini of the beta-sheet strands and the subsequent alpha-helices. They do not face each other, making "channeling" of the substrate between active sites virtually impossible. Despite the structural similarity of the two domains, no significant sequence homology was found when topologically equivalent residues were compared.
authors.forename: J P
authors.initials: JP
authors.lastname: Priestle
authors.forename: M G
authors.initials: MG
authors.lastname: Grütter
authors.forename: J L
authors.initials: JL
authors.lastname: White
authors.forename: M G
authors.initials: MG
authors.lastname: Vincent
authors.forename: M
authors.initials: M
authors.lastname: Kania
authors.forename: E
authors.initials: E
authors.lastname: Wilson
authors.forename: T S
authors.initials: TS
authors.lastname: Jardetzky
authors.forename: K
authors.initials: K
authors.lastname: Kirschner
authors.forename: J N
authors.initials: JN
authors.lastname: Jansonius
mesh_terms: D019747:Aldose-Ketose Isomerases; D000595:Amino Acid Sequence; D001665:Binding Sites; D002238:Carbohydrate Epimerases; D002262:Carboxy-Lyases; D004926:Escherichia coli / Q000201:enzymology*; D007209:Indole-3-Glycerol-Phosphate Synthase; D046911:Macromolecular Substances; D008970:Molecular Weight; D009097:Multienzyme Complexes; D010449:Peptide Mapping; D014364:Tryptophan / Q000096:biosynthesis; D014961:X-Ray Diffraction
chemical_list: D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D014364:Tryptophan; D002262:Carboxy-Lyases; D007209:Indole-3-Glycerol-Phosphate Synthase; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; C029865:phosphoribosylanthranilate isomerase