Open AccessThree-dimensional structure of the bifunctional enzyme N-(5'-phosphoribosyl)anthranilate isomerase-indole-3-glycerol-phosphate synthase from Escherichia coli.
Author(s) -
John P. Priestle,
M.G. Grütter,
Janice L. White,
M. G. Vincent,
Malgosia Kania,
Eileen Wilson,
Theodore S. Jardetzky,
Kasper Kirschner,
Johan N. Jansonius
Publication year - 1987
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.84.16.5690
Subject(s) - tryptophan synthase , isomerase , stereochemistry , escherichia coli , phosphofructokinase 2 , active site , atp synthase , chemistry , triosephosphate isomerase , enzyme , biochemistry , indole test , bifunctional , biosynthesis , substrate (aquarium) , biology , catalysis , ecology , gene
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.