Human Thymidylate Synthase Stabilized in Active Conformation by R163K Mutation: Asymmetry and Reactivity of Cys195

Experimental Data Snapshot

  • Resolution: 2.67 Å
  • R-Value Free: 0.279 
  • R-Value Work: 0.209 
  • R-Value Observed: 0.212 

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This is version 1.4 of the entry. See complete history


The R163K mutant of human thymidylate synthase is stabilized in an active conformation: structural asymmetry and reactivity of cysteine 195.

Gibson, L.M.Lovelace, L.L.Lebioda, L.

(2008) Biochemistry 47: 4636-4643

  • DOI: https://doi.org/10.1021/bi7019386
  • Primary Citation of Related Structures:  
    2RD8, 2RDA

  • PubMed Abstract: 

    Loop 181-197 of human thymidylate synthase (hTS) populates two conformational states. In the first state, Cys195, a residue crucial for catalytic activity, is in the active site (active conformer); in the other conformation, it is about 10 A away, outside the active site (inactive conformer). We have designed and expressed an hTS variant, R163K, in which the inactive conformation is destabilized. The activity of this mutant is 33% higher than that of wt hTS, suggesting that at least one-third of hTS populates the inactive conformer. Crystal structures of R163K in two different crystal forms, with six and two subunits per asymmetric part of the unit cells, have been determined. All subunits of this mutant are in the active conformation while wt hTS crystallizes as the inactive conformer in similar mother liquors. The structures show differences in the environment of catalytic Cys195, which correlate with Cys195 thiol reactivity, as judged by its oxidation state. Calculations show that the molecular electrostatic potential at Cys195 differs between the subunits of the dimer. One of the dimers is asymmetric with a phosphate ion bound in only one of the subunits. In the absence of the phosphate ion, that is in the inhibitor-free enzyme, the tip of loop 47-53 is about 11 A away from the active site.

  • Organizational Affiliation

    Department of Chemistry and Biochemistry and Center for Colon Cancer Research, University of South Carolina, Columbia, SC 29208, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Thymidylate synthase
A, B, C, D, E
A, B, C, D, E, F
313Homo sapiensMutation(s): 1 
Gene Names: TYMSTS
UniProt & NIH Common Fund Data Resources
Find proteins for P04818 (Homo sapiens)
Explore P04818 
Go to UniProtKB:  P04818
PHAROS:  P04818
GTEx:  ENSG00000176890 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP04818
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.67 Å
  • R-Value Free: 0.279 
  • R-Value Work: 0.209 
  • R-Value Observed: 0.212 
  • Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 123.794α = 90
b = 123.794β = 90
c = 284.766γ = 120
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling
PDB_EXTRACTdata extraction
HKL-2000data collection
HKL-2000data reduction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2008-06-10
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2017-10-25
    Changes: Refinement description
  • Version 1.3: 2021-10-20
    Changes: Database references, Derived calculations
  • Version 1.4: 2023-08-30
    Changes: Data collection, Refinement description