Structural and thermodynamic properties of kappa class glutathione transferase from Camelus dromedarius

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International journal of biological macromolecules
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tThe Arabian camel, Camelus dromedarius is naturally adapted to extreme desert climate and has evolvedprotective mechanisms to limit oxidative stress. The mitochondrial kappa class glutathione transferaseenzyme is a member of GST supergene family that represents an important enzyme group in cellular PhaseII detoxification machinery and is involved in the protection against oxidative stress and xenobiotics. Inthe present study, C. dromedarius kappa class glutathione transferase (CdGSTK1-1) was cloned, expressedin E. coli BL21, purified and its structural, thermodynamic and unfolding pathway was investigated. Theresults showed that CdGSTK1-1 has unique trimeric structure, exhibits low thermostability and a complexequilibrium unfolding profile. It unfolds through three folding states with formation of thinly populatedintermediate species. The melting points (Tm) of the first unfolding transition was 40.3 ± 0.2◦C and Tm ofthe second unfolding transition was 49.1 ± 0.1◦C. The van’t Hoff enthalpy of the first and second transitionwere 298.7 ± 13.2 and 616.5 ± 2.4 kJ/mol, respectively. Moreover, intrinsic fluorescence and near-UV CDstudies indicates that substrate binding does not leads to major conformational changes in CdGSTK1-1.