2tsc
From Proteopedia
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STRUCTURE, MULTIPLE SITE BINDING, AND SEGMENTAL ACCOMODATION IN THYMIDYLATE SYNTHASE ON BINDING D/UMP AND AN ANTI-FOLATE
Overview
The structure of Escherichia coli thymidylate synthase (TS) complexed with, the substrate dUMP and an analogue of the cofactor, methylenetetrahydrofolate was solved by multiple isomorphous replacement, and refined at 1.97-A resolution to a residual of 18% for all data (16%, for data greater than 2 sigma) for a highly constrained structure. All, residues in the structure are clearly resolved and give a very high, confidence in total correctness of the structure. The ternary complex, directly suggests how methylation of dUMP takes place. C-6 of dUMP is, covalently bound to gamma S of Cys-198(146) during catalysis, and the, reactants are surrounded by specific hydrogen bonds and hydrophobic, interactions from conserved residues. Comparison with the independently, solved structure of unliganded TS reveals a large conformation change in, the enzyme, which closes down to sequester the reactants and several, highly ordered water molecules within a cavernous active center, away from, bulk solvent. A second binding site for the quinazoline ring of the, cofactor analogue was discovered by withholding addition of reducing agent, during crystal storage. The chemical change in the protein is slight, and, from difference density maps modification of sulfhydryls is not directly, responsible for blockade of the primary site. The site, only partially, overlapping with the primary site, is also surrounded by conserved, residues and thus may play a functional role. The ligand-induced, conformational change is not a domain shift but involves the segmental, accommodation of several helices, beta-strands, and loops that move as, units against the beta-sheet interface between monomers.
About this Structure
2TSC is a Single protein structure of sequence from Escherichia coli with UMP and CB3 as ligands. Active as Thymidylate synthase, with EC number 2.1.1.45 Full crystallographic information is available from OCA.
Reference
Structure, multiple site binding, and segmental accommodation in thymidylate synthase on binding dUMP and an anti-folate., Montfort WR, Perry KM, Fauman EB, Finer-Moore JS, Maley GF, Hardy L, Maley F, Stroud RM, Biochemistry. 1990 Jul 31;29(30):6964-77. PMID:2223754
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