1HW4

STRUCTURE OF THYMIDYLATE SYNTHASE SUGGESTS ADVANTAGES OF CHEMOTHERAPY WITH NONCOMPETITIVE INHIBITORS

Summary for 1HW4

• Entry DOI: 10.2210/pdb1hw4/pdb
• Related: 1HW3
• Descriptor: THYMIDYLATE SYNTHASE, SULFATE ION, 1,2-ETHANEDIOL, ... (4 entities in total)
• Functional Keywords: thymidylate synthase, methyltransferase, transferase
• Biological source: Homo sapiens (human)
• Total number of polymer chains: 1
• Total formula weight: 41267.14

Authors

Phan, J.,Steadman, J.D.,Koli, S.,Ding, W.C.,Minor, W.,Dunlap, R.B.,Berger, S.H.,Lebioda, L. (deposition date: 2001-01-09, release date: 2001-01-24, Last modification date: 2024-10-16)

Primary citation

Phan, J.,Steadman, D.J.,Koli, S.,Ding, W.C.,Minor, W.,Dunlap, R.B.,Berger, S.H.,Lebioda, L.
Structure of human thymidylate synthase suggests advantages of chemotherapy with noncompetitive inhibitors.
J.Biol.Chem., 276:14170-14177, 2001

PubMed Abstract: Thymidylate synthase (TS) is a major target in the chemotherapy of colorectal cancer and some other neoplasms. The emergence of resistance to the treatment is often related to the increased levels of TS in cancer cells, which have been linked to the elimination of TS binding to its own mRNA upon drug binding, a feedback regulatory mechanism, and/or to the increased stability to intracellular degradation of TS.drug complexes (versus unliganded TS). The active site loop of human TS (hTS) has a unique conformation resulted from a rotation by 180 degrees relative to its orientation in bacterial TSs. In this conformation, the enzyme must be inactive, because the catalytic cysteine is no longer positioned in the ligand-binding pocket. The ordered solvent structure obtained from high resolution crystallographic data (2.0 A) suggests that the inactive loop conformation promotes mRNA binding and intracellular degradation of the enzyme. This hypothesis is supported by fluorescence studies, which indicate that in solution both active and inactive forms of hTS are present. The binding of phosphate ion shifts the equilibrium toward the inactive conformation; subsequent dUMP binding reverses the equilibrium toward the active form. Thus, TS inhibition via stabilization of the inactive conformation should lead to less resistance than is observed with presently used drugs, which are analogs of its substrates, dUMP and CH(2)H(4)folate, and bind in the active site, promoting the active conformation. The presence of an extension at the N terminus of native hTS has no significant effect on kinetic properties or crystal structure.

PubMed: 11278511

Experimental method

X-RAY DIFFRACTION (2.06 Å)