2TDD: Structures Of Thymidylate Synthase With A C-Terminal Deletion: Role Of The C-Terminus In Alignment Of DUMP AND CH2H4FOLATE

Thymidylate synthase undergoes a major conformational change upon ligand binding, where the carboxyl terminus displays the largest movement (approximately 4 A). This movement from an "open" unliganded state to the "closed" complexed conformation plays a crucial role in the correct orientation of substrates and in product formation. The mutant lacking the C-terminal valine (V316Am) of the enzyme is inactive. X-ray crystal structures of V316Am and its complexes with dUMP, FdUMP, and both FdUMP and CH2H4folate are described. The structures show that ligands are bound within the active site, but in different modes than those in analogous, wild-type thymidylate synthase structures. The 2.7-A binary complex structures of V316Am with FdUMP and dUMP show that the pyrimidine and ribose moieties of the nucleotides are pivoted approximately 20 degrees around the 3'-hydroxyl compared to dUMP in the wild-type enzyme. The 2.7-A crystal structure of V316Am complexed with cofactor, CH2H4folate, and the substrate analog, FdUMP, shows these ligands bound in an open conformation similar to that of the unliganded enzyme. In this ternary complex, the imidazolidine ring of the cofactor is open and has reacted with water to form 5-HOCH2H4folate. 5-HOCH2H4folate is structural evidence for the 5-iminium ion intermediate, which is the proposed reactive form of CH2H4folate. The altered ligand binding modes observed in the three V316Am complex structures open new venues for the design of novel TS inhibitors.
PDB ID: 2TDDDownload
MMDB ID: 58230
PDB Deposition Date: 1993/4/5
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 2.7  Å
Source Organism:
Similar Structures:
Biological Unit for 2TDD: dimeric; determined by author and by software (PISA,PQS)
Molecular Components in 2TDD
Label Count Molecule
Proteins (2 molecules)
Thymidylate Synthase
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB