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'''STRUCTURES OF THYMIDYLATE SYNTHASE WITH A C-TERMINAL DELETION: ROLE OF THE C-TERMINUS IN ALIGNMENT OF D/UMP AND CH2H4FOLATE''' | '''STRUCTURES OF THYMIDYLATE SYNTHASE WITH A C-TERMINAL DELETION: ROLE OF THE C-TERMINUS IN ALIGNMENT OF D/UMP AND CH2H4FOLATE''' | ||
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[[Category: Santi, D V.]] | [[Category: Santi, D V.]] | ||
[[Category: Stroud, R M.]] | [[Category: Stroud, R M.]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 09:48:55 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 09:48, 3 May 2008
STRUCTURES OF THYMIDYLATE SYNTHASE WITH A C-TERMINAL DELETION: ROLE OF THE C-TERMINUS IN ALIGNMENT OF D/UMP AND CH2H4FOLATE
OverviewOverview
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.
About this StructureAbout this Structure
1TDA is a Single protein structure of sequence from Lactobacillus casei. Full crystallographic information is available from OCA.
ReferenceReference
Structures of thymidylate synthase with a C-terminal deletion: role of the C-terminus in alignment of 2'-deoxyuridine 5'-monophosphate and 5,10-methylenetetrahydrofolate., Perry KM, Carreras CW, Chang LC, Santi DV, Stroud RM, Biochemistry. 1993 Jul 20;32(28):7116-25. PMID:8343503 Page seeded by OCA on Sat May 3 09:48:55 2008