Role of Ser11 in the stabilization of the structure of Ochrobactrum anthropi glutathione transferase

Luca Federici , Michele Masulli , Daniele Bonivento , Adele Di Matteo , Stefano Gianni , Bartolo Favaloro , Carmine Di Ilio , Nerino Allocati (1)

1 Scienze Biomediche

Glutathione transferases (GSTs) are a multifunctional group of enzymes, widely distributed and involved in cellular detoxification processes. In the xenobiotic degrading bacterium Ochrobactrum anthropi, GST is overexpressed in the presence of toxic concentrations of aromatic compounds such as 4-chlorophenol and atrazine. We have determined the crystal structure of the GST from O. anthropi (OaGST) in complex with GSH. Like other bacterial GSTs, OaGST belongs to the beta class and shows a similar binding pocket for GSH. However, in contrast with the structure of Proteus mirabilis GST, GSH is not covalently bound to Cys 10} but is present in the thiolate form. In our investigation of the structural basis for GSH stabilization we have identified a conserved network of hydrogen-bond interactions, mediated by the presence of a structural water molecule that links Ser 11} to Glu 198}. Partial disruption of this network, by mutagenesis of Ser 11} to Ala, increases the K m} for GSH by 15 fold and decreases the catalytic efficiency by 4 fold, even though Ser 11} is not involved in GSH binding. Thermal and chemical induced unfolding studies point to a global effect of the mutation on the stability of the protein and to a central role of these residues in zippering the terminal helix of the C-terminal domain to the starting helix of the N-terminal domain.

Mots clés: Life Sciences

Luca Federici, Michele Masulli, Daniele Bonivento, Adele Di Matteo, Stefano Gianni, et al.. Role of Ser11 in the stabilization of the structure of Ochrobactrum anthropi glutathione transferase. Biochemical Journal, 2007, 403 (2), pp.267-274. ⟨10.1042/BJ20061707⟩. ⟨hal-00478695⟩