Crystal structure of selenomethionine labelled gama glutamyl cyclotransferease specific to glutathione from yeast

Experimental Data Snapshot

  • Resolution: 1.75 Å
  • R-Value Free: 0.210 
  • R-Value Work: 0.168 
  • R-Value Observed: 0.170 

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ChaC2, an Enzyme for Slow Turnover of Cytosolic Glutathione

Kaur, A.Gautam, R.Srivastava, R.Chandel, A.Kumar, A.Karthikeyan, S.Bachhawat, A.K.

(2017) J Biol Chem 292: 638-651

  • DOI: https://doi.org/10.1074/jbc.M116.727479
  • Primary Citation of Related Structures:  
    5HWI, 5HWK

  • PubMed Abstract: 

    Glutathione degradation plays an important role in glutathione and redox homeostasis, and thus it is imperative to understand the enzymes and the mechanisms involved in glutathione degradation in detail. We describe here ChaC2, a member of the ChaC family of γ-glutamylcyclotransferases, as an enzyme that degrades glutathione in the cytosol of mammalian cells. ChaC2 is distinct from the previously described ChaC1, to which ChaC2 shows ∼50% sequence identity. Human and mouse ChaC2 proteins purified in vitro show 10-20-fold lower catalytic efficiency than ChaC1, although they showed comparable K m values (K m of 3.7 ± 0.4 mm and k cat of 15.9 ± 1.0 min -1 toward glutathione for human ChaC2; K m of 2.2 ± 0.4 mm and k cat of 225.2 ± 15 min -1 toward glutathione for human ChaC1). The ChaC1 and ChaC2 proteins also shared the same specificity for reduced glutathione, with no activity against either γ-glutamyl amino acids or oxidized glutathione. The ChaC2 proteins were found to be expressed constitutively in cells, unlike the tightly regulated ChaC1. Moreover, lower eukaryotes have a single member of the ChaC family that appears to be orthologous to ChaC2. In addition, we determined the crystal structure of yeast ChaC2 homologue, GCG1, at 1.34 Å resolution, which represents the first structure of the ChaC family of proteins. The catalytic site is defined by a fortuitous benzoic acid molecule bound to the crystal structure. The mechanism for binding and catalytic activity of this new enzyme of glutathione degradation, which is involved in continuous but basal turnover of cytosolic glutathione, is proposed.

  • Organizational Affiliation

    From the Department of Biological Sciences, Indian Institute of Science Education and Research, Mohali, S.A.S. Nagar, Punjab 140306, India and.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Glutathione-specific gamma-glutamylcyclotransferase240Saccharomyces cerevisiae S288CMutation(s): 4 
Gene Names: GCG1
EC: 2.3.2
Find proteins for P32656 (Saccharomyces cerevisiae (strain ATCC 204508 / S288c))
Explore P32656 
Go to UniProtKB:  P32656
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP32656
Sequence Annotations
  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on MSE
Experimental Data & Validation

Experimental Data

  • Resolution: 1.75 Å
  • R-Value Free: 0.210 
  • R-Value Work: 0.168 
  • R-Value Observed: 0.170 
  • Space Group: P 42 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 110.545α = 90
b = 110.545β = 90
c = 42.592γ = 90
Software Package:
Software NamePurpose
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Department of Science and TechnologyIndiaSB/SO/BB/017/2014

Revision History  (Full details and data files)

  • Version 1.0: 2016-12-14
    Type: Initial release
  • Version 1.1: 2017-01-25
    Changes: Database references