title: Human thymidylate synthase is in the closed conformation when complexed with dUMP and raltitrexed, an antifolate drug.
abstract: Thymidylate synthase (TS) is a major target in the chemotherapy of colorectal cancer and some other neoplasms while raltitrexed (Tomudex, ZD1694) is an antifolate inhibitor of TS approved for clinical use in several European countries. The crystal structure of the complex between recombinant human TS, dUMP, and raltitrexed has been determined at 1.9 A resolution. In contrast to the situation observed in the analogous complex of the rat TS, the enzyme is in the closed conformation and a covalent bond between the catalytic Cys 195 and dUMP is present in both subunits. This mode of ligand binding is similar to that of the analogous complex of the Escherichia coli enzyme. The only major differences observed are a direct hydrogen bond between His 196 and the O4 atom of dUMP and repositioning of the side chain of Tyr 94 by about 2 A. The thiophene ring of the drug is disordered between two parallel positions.
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 92908, USA.
authors.forename: J
authors.initials: J
authors.lastname: Phan
authors.forename: S
authors.initials: S
authors.lastname: Koli
authors.forename: W
authors.initials: W
authors.lastname: Minor
authors.forename: R B
authors.initials: RB
authors.lastname: Dunlap
authors.forename: S H
authors.initials: SH
authors.lastname: Berger
authors.forename: L
authors.initials: L
authors.lastname: Lebioda
mesh_terms: D001665:Binding Sites; D003198:Computer Simulation; D003460:Crystallization; D018360:Crystallography, X-Ray; D003856:Deoxyuracil Nucleotides / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D004791:Enzyme Inhibitors / Q000737:chemistry*; D005493:Folic Acid Antagonists / Q000737:chemistry*; D006801:Humans; D008024:Ligands; D046911:Macromolecular Substances; D008958:Models, Molecular; D011487:Protein Conformation; D011799:Quinazolines / Q000737:chemistry* / Q000378:metabolism; D013876:Thiophenes / Q000737:chemistry* / Q000378:metabolism; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism
chemical_list: D003856:Deoxyuracil Nucleotides; D004791:Enzyme Inhibitors; D005493:Folic Acid Antagonists; D008024:Ligands; D046911:Macromolecular Substances; D011799:Quinazolines; D013876:Thiophenes; C007267:2'-deoxyuridylic acid; D013940:Thymidylate Synthase; C068874:raltitrexed