Saccharomyces cerevisiae cells have three Omega class glutathione S-transferases acting as 1-Cys thiol transferases

Abstract

The Saccharomyces cerevisiae genome encodes three proteins that display similarities with human GSTOs (Omega class glutathione S-transferases) hGSTO1-1 and hGSTO2-2. The three yeast proteins have been named Gto1, Gto2 and Gto3, and their purified recombinant forms are active as thiol transferases (glutaredoxins) against HED (beta-hydroxyethyl disulphide), as dehydroascorbate reductases and as dimethylarsinic acid reductases, while they are not active against the standard GST substrate CDNB (1-chloro-2,4-dinitrobenzene). Their glutaredoxin activity is also detectable in yeast cell extracts. The enzyme activity characteristics of the Gto proteins contrast with those of another yeast GST, Gtt1. The latter is active against CDNB and also displays glutathione peroxidase activity against organic hydroperoxides such as cumene hydroperoxide, but is not active as a thiol transferase. Analysis of point mutants derived from wild-type Gto2 indicates that, among the three cysteine residues of the molecule, only the residue at position 46 is required for the glutaredoxin activity. This indicates that the thiol transferase acts through a monothiol mechanism. Replacing the active site of the yeast monothiol glutaredoxin Grx5 with the proposed Gto2 active site containing Cys46 allows Grx5 to retain some activity against HED. Therefore the residues adjacent to the respective active cysteine residues in Gto2 and Grx5 are important determinants for the thiol transferase activity against small disulphide-containing molecules.

A novel Omega-class glutathione S-transferase gene in Apis cerana cerana: molecular characterisation of GSTO2 and its protective effects in oxidative stress

“…Unlike most GSTOs, the recombinant AccGSTO2 had DHAR activity and GSH-dependent peroxidase activity, and it also catalysed the conjugation of CDNB. These results were consistent with two recent studies by Burmeister et al (2008) and Garcera et al (2006). The precise mechanism involved in the distinct enzymatic features has not yet been elucidated.…”

“…To date, GSTOs appear to be widespread in nature and have been identified in plants (Dixon et al 2002), yeast (Garcera et al 2006), insects (Walters et al 2009), bacteria (Xun et al 2010), and mammals (Rouimi et al 2001). GSTOs have unique structural and functional characteristics.…”

LeishmaniaTDR1 structure, a unique trimeric glutathione transferase capable of deglutathionylation and antimonial prodrug activation

“…Critically, TDR1 can reduce protein-glutathione adducts. A role in redox-regulation by deglutathionylation of protein-GSH mixed disulfides has been proposed for glutaredoxins (11,20,21), omega class GSTs (19) and the GST-like glutaredoxins including Escherichia coli GRX2 (22). TDR1 is able to catalyze the deglutathionylation of both small molecule mixed-disulfides and glutathionylated bovine serum albumin as efficiently as LiGRX1 (Table 1, Table S2).…”

“…Some GSTs, for example, yeast omega-GST, possess peroxidise activities (19). TDR1 does not (Table 1).…”

“…A series of enzyme assays, using published methods, were carried out to assess TDR1 for thioltransferase, disulfide reductase, peroxidase, and peptide deglutathionylation activities (15,16,19,20).…”