2OGT

Crystal Structure of the Geobacillus Stearothermophilus Carboxylesterase EST55 at pH 6.8


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.58 Å
  • R-Value Free: 0.241 
  • R-Value Work: 0.173 
  • R-Value Observed: 0.173 

Starting Model: experimental
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This is version 1.5 of the entry. See complete history


Literature

Crystal Structure of the Geobacillus stearothermophilus Carboxylesterase Est55 and Its Activation of Prodrug CPT-11.

Liu, P.Ewis, H.E.Tai, P.C.Lu, C.D.Weber, I.T.

(2007) J Mol Biol 367: 212-223

  • DOI: https://doi.org/10.1016/j.jmb.2006.12.067
  • Primary Citation of Related Structures:  
    2OGS, 2OGT

  • PubMed Abstract: 

    Several mammalian carboxylesterases were shown to activate the prodrug irinotecan (CPT-11) to produce 7-ethyl-10-hydroxycamptothecin (SN-38), a topoisomerase inhibitor used in cancer therapy. However, the potential use of bacterial carboxylesterases, which have the advantage of high stability, has not been explored. We present the crystal structure of the carboxyesterase Est55 from Geobacillus stearothermophilus and evaluation of its enzyme activity on CPT-11. Crystal structures were determined at pH 6.2 and pH 6.8 and resolution of 2.0 A and 1.58 A, respectively. Est55 folds into three domains, a catalytic domain, an alpha/beta domain and a regulatory domain. The structure is in an inactive form; the side-chain of His409, one of the catalytic triad residues, is directed away from the other catalytic residues Ser194 and Glu310. Moreover, the adjacent Cys408 is triply oxidized and lies in the oxyanion hole, which would block the binding of substrate, suggesting a regulatory role. However, Cys408 is not essential for enzyme activity. Mutation of Cys408 showed that hydrophobic side-chains were favorable, while polar serine was unfavorable for enzyme activity. Est55 was shown to hydrolyze CPT-11 into the active form SN-38. The mutant C408V provided a more stable enzyme for activation of CPT-11. Therefore, engineered thermostable Est55 is a candidate for use with irinotecan in enzyme-prodrug cancer therapy.


  • Organizational Affiliation

    Department of Biology, Molecular Basis of Disease Program, Georgia State University, Atlanta, GA 30303, USA.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Thermostable carboxylesterase Est50498Geobacillus stearothermophilusMutation(s): 0 
EC: 3.1.1.1
UniProt
Find proteins for Q8GCC7 (Geobacillus stearothermophilus)
Explore Q8GCC7 
Go to UniProtKB:  Q8GCC7
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ8GCC7
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.58 Å
  • R-Value Free: 0.241 
  • R-Value Work: 0.173 
  • R-Value Observed: 0.173 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 69.361α = 90
b = 74.43β = 90
c = 98.606γ = 90
Software Package:
Software NamePurpose
SHELXL-97refinement
CNSrefinement
CCP4model building
MAR345data collection
HKL-2000data scaling
CCP4phasing
CNSphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2007-02-13
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Non-polymer description, Version format compliance
  • Version 1.3: 2017-10-18
    Changes: Advisory, Refinement description
  • Version 1.4: 2019-07-24
    Changes: Data collection, Refinement description
  • Version 1.5: 2023-08-30
    Changes: Advisory, Data collection, Database references, Derived calculations, Refinement description