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Variants of Human Thymidylate Synthase with Loop 181–197 Stabilized in the Inactive Conformation by Leslie L. Lovelace; Saphronia R. Johnson; Lydia M. Gibson; Brittnaie J. Bell; Sondra H. Berger; Lukasz Lebioda is a Biochemistry, Genetics and Molecular Biology article available to read on EtoBox.

What is Variants of Human Thymidylate Synthase with Loop 181–197 Stabilized in the Inactive Conformation about?

## Abstract Loop 181–197 of human thymidylate synthase (hTS) populates two major conformations, essentially corresponding to the loop flipped by 180°. In one of the conformations, the catalytic Cys195 residue lies distant from the active site making the enzyme inactive. Ligands stabilizing this inactive conformation may function as allosteric inhibitors. To facilitate the search for such inhibitors, we have expressed and characterized several mutants designed to shift the equilibrium toward the inactive conformer. In most cases, the catalytic efficiency of the mutants was only somewhat impaired with values of __k__~cat~/__K__~m~ reduced by factors in a 2–12 range. One of the mutants, M190K, is however unique in having the value of __k__~cat~/__K__~m~ smaller by a factor of ∼7500 than the wild type. The crystal structure of this mutant is similar to that of the __wt__ hTS with loop 181–197 in the inactive conformation. However, the direct vicinity of the mutation, residues 188–194 of this loop, assumes a different conformation with the positions of C~α~ shifted up to 7.2 Å. This affects region 116–128, which became ordered in M190K while it is disordered in __wt__. The conformation

Who reads Variants of Human Thymidylate Synthase with Loop 181–197 Stabilized in the Inactive Conformation?

Author

Leslie L. Lovelace; Saphronia R. Johnson; Lydia M. Gibson; Brittnaie J. Bell; Sondra H. Berger; Lukasz Lebioda

Publisher

Cold Spring Harbor Laboratory Press; Wiley (John Wiley & Sons); Wiley-Blackwell; Wiley (ISSN 0961-8368)

Published

2009

Language

EN

Field

Biochemistry, Genetics and Molecular Biology (Life Sciences)