1i00

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CRYSTAL STRUCTURE OF HUMAN THYMIDYLATE SYNTHASE, TERNARY COMPLEX WITH DUMP AND TOMUDEX

Contents 1 Overview 2 Disease 3 About this Structure 4 Reference

Overview

The crystal structures of a deletion mutant of human thymidylate synthase, (TS) and its ternary complex with dUMP and Tomudex have been determined at, 2.0 A and 2.5 A resolution, respectively. The mutant TS, which lacks 23, residues near the amino terminus, is as active as the wild-type enzyme., The ternary complex is observed in the open conformation, similar to that, of the free enzyme and to that of the ternary complex of rat TS with the, same ligands. This is in contrast to Escherichia coli TS, where the, ternary complex with Tomudex and dUMP is observed in the closed, conformation. While the ligands interact with each other in identical, fashion regardless of the enzyme conformation, they are displaced by about, 1.0 A away from the catalytic cysteine in the open conformation. As a, result, the covalent bond between the catalytic cysteine sulfhydryl and, the base of dUMP, which is the first step in the reaction mechanism of TS, and is observed in all ternary complexes of the E. coli enzyme, is not, formed. This displacement results from differences in the interactions, between Tomudex and the protein that are caused by differences in the, environment of the glutamyl tail of the Tomudex molecule. Despite the, absence of the closed conformation, Tomudex inhibits human TS ten-fold, more strongly than E. coli TS. These results suggest that formation of a, covalent bond between the catalytic cysteine and the substrate dUMP is not, required for effective inhibition of human TS by cofactor analogs and, could have implications for drug design by eliminating this as a condition, for lead compounds.

Disease

Known disease associated with this structure: Timothy syndrome OMIM:[114205]

About this Structure

1I00 is a Single protein structure of sequence from Homo sapiens with UMP and D16 as ligands. Active as Thymidylate synthase, with EC number 2.1.1.45 Full crystallographic information is available from OCA.

Reference

Crystal structure of a deletion mutant of human thymidylate synthase Delta (7-29) and its ternary complex with Tomudex and dUMP., Almog R, Waddling CA, Maley F, Maley GF, Van Roey P, Protein Sci. 2001 May;10(5):988-96. PMID:11316879

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