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Cofactor triggers the conformational change in thymidylate synthase: implications for an ordered binding mechanism
A Kamb1, J S Finer-Moore, R M Stroud
1Department of Biochemistry and Biophysics, University of California, San Francisco 94143.
Biochemistry
|December 29, 1992
Summary
Crystal structures reveal that Escherichia coli thymidylate synthase (TS) undergoes conformational changes upon cofactor binding alone. This suggests a key intermediate in the TS reaction pathway, with implications for drug development.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Thymidylate synthase (TS) is a crucial enzyme in DNA synthesis.
- Understanding TS conformational changes is vital for developing targeted therapies.
Purpose of the Study:
- To elucidate the structural basis of thymidylate synthase conformational changes upon cofactor binding.
- To investigate the accessibility of the dUMP binding site in TS-cofactor complexes.
Main Methods:
- X-ray crystallography was used to determine the structures of two TS-cofactor analog complexes.
- Complexes studied included those with N10-propargyl-5,8-dideazafolate (CB3717) and its polygutamyl derivative.
Main Results:
- Cofactor binding alone induces a conformational change in TS, independent of dUMP binding.
- The dUMP binding site remains accessible in TS-cofactor binary complexes.
- Polyglutamyl folates, the in vivo cofactor form, bind more tightly than dUMP.
Conclusions:
- The determined structures represent a key intermediate in the TS reaction pathway.
- Conformational flexibility allows dUMP entry into the active site while the cofactor is bound.
- dUMP may enter via a distinct portal, facilitating binding to the catalytically competent TS-cofactor complex.