Crystal structure of the bifunctional chorismate synthase from Saccharomyces cerevisiae.
Chorismate synthase (EC 4.2.3.5), the seventh enzyme in the shikimate pathway, catalyzes the transformation of 5-enolpyruvylshikimate 3-phosphate (EPSP) to chorismate, which is the last common precursor in the biosynthesis of numerous aromatic compounds in bacteria, fungi, and plants. The chorismate synthase reaction involves a 1,4-trans-elimination of phosphoric acid from EPSP and has an absolute requirement for reduced FMN as a cofactor. We have determined the three-dimensional x-ray structure of the yeast chorismate synthase from selenomethionine-labeled crystals at 2.2-A resolution. The structure shows a novel betaalphabetaalpha fold consisting of an alternate tight packing of two alpha-helical and two beta-sheet layers, showing no resemblance to any documented protein structure. The molecule is arranged as a tight tetramer with D2 symmetry, in accordance with its quaternary structure in solution. Electron density is missing for 23% of the amino acids, spread over sequence regions that in the three-dimensional structure converge on the surface of the protein. Many totally conserved residues are contained within these regions, and they probably form a structured but mobile domain that closes over a cleft upon substrate binding and catalysis. This hypothesis is supported by previously published spectroscopic measurements implying that the enzyme undergoes considerable structural changes upon binding of both FMN and EPSP.
Quevillon-Cheruel
Sophie
S
Institut de Biochimie et de Biophysique Moléculaire et Cellulaire (CNRS-UMR 8619), Université Paris-Sud, Bâtiment 430, 91405 Orsay, France.
Leulliot
Nicolas
N
Meyer
Philippe
P
Graille
Marc
M
Bremang
Michael
M
Blondeau
Karine
K
Sorel
Isabelle
I
Poupon
Anne
A
Janin
Joël
J
van Tilbeurgh
Herman
H
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019761:Phosphorus-Oxygen Lyases / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D012680:Sensitivity and Specificity; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D011994:Recombinant Proteins; C019895:chorismate synthase; D019761:Phosphorus-Oxygen Lyases