Structure and Function of YghU, a Nu-Class Glutathione Transferase Related to YfcG from Escherichia coli

Department of Biochemistry, Center in Molecular Toxicology, and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232-0146, United States.
Biochemistry (Impact Factor: 3.02). 02/2011; 50(7):1274-81. DOI: 10.1021/bi101861a
Source: PubMed


The crystal structure (1.50 Å resolution) and biochemical properties of the GSH transferase homologue, YghU, from Escherichia coli reveal that the protein is unusual in that it binds two molecules of GSH in each active site. The crystallographic observation is consistent with biphasic equilibrium binding data that indicate one tight (K(d1) = 0.07 ± 0.03 mM) and one weak (K(d2) = 1.3 ± 0.2 mM) binding site for GSH. YghU exhibits little or no GSH transferase activity with most typical electrophilic substrates but does possess a modest catalytic activity toward several organic hydroperoxides. Most notably, the enzyme also exhibits disulfide-bond reductase activity toward 2-hydroxyethyl disulfide [k(cat) = 74 ± 6 s(-1), and k(cat)/K(M)(GSH) = (6.6 ± 1.3) × 10(4) M(-1) s(-1)] that is comparable to that previously determined for YfcG. A superposition of the structures of the YghU·2GSH and YfcG·GSSG complexes reveals a remarkable structural similarity of the active sites and the 2GSH and GSSG molecules in each. We conclude that the two structures represent reduced and oxidized forms of GSH-dependent disulfide-bond oxidoreductases that are distantly related to glutaredoxin 2. The structures and properties of YghU and YfcG indicate that they are members of the same, but previously unidentified, subfamily of GSH transferase homologues, which we suggest be called the nu-class GSH transferases.

  • Source
    • "In Aspergillus nidulans, the GSTA mutant is sensitive to xenobiotics and heavy metals [20] and in P. chrysosporium, the expression of PcUre2pB1 is upregulated in presence of nonylphenol [21]. In bacteria, EcYfcG might interact with glutathionylspermidin and perhaps utilizes it as a substrate or a regulatory molecule [3] [4]. However, the physiological targets (substrates and proteins) of these microbial specific proteins remain to be identified and will help to decipher their physiological roles. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Glutathione transferases (GSTs) are known to transfer glutathione onto small hydrophobic molecules in detoxification reactions. The GST Ure2pB1 from Phanerochaete chrysosporium exhibits atypical features, ie the presence of two glutathione binding sites and a high affinity towards oxidized glutathione. Moreover, PcUre2pB1 is able to efficiently deglutathionylate GS-phenacylacetophenone. Catalysis is not mediated by the cysteines of the protein but rather by the one of glutathione and an asparagine residue plays a key role in glutathione stabilization. Interestingly PcUre2pB1 interacts in vitro with a GST of the omega class. These properties are discussed in the physiological context of wood degrading fungi.
    Preview · Article · May 2013 · FEBS letters
  • Source
    • "Two isoforms (YfcG and YchU) have been characterized in Escherichia coli (Kanai et al., 2006). Both have thiol disulfide oxidoreductase activity and contrary to the yeast isoform, weak GST and peroxidase activities (Wadington et al., 2009; Stourman et al., 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Fungal degradation of wood is mainly restricted to basidiomycetes, these organisms having developed complex oxidative and hydrolytic enzymatic systems. Besides these systems, wood-decaying fungi possess intracellular networks allowing them to deal with the myriad of potential toxic compounds resulting at least in part from wood degradation but also more generally from recalcitrant organic matter degradation. The members of the detoxification pathways constitute the xenome. Generally, they belong to multigenic families such as the cytochrome P450 monooxygenases and the glutathione transferases. Taking advantage of the recent release of numerous genomes of basidiomycetes, we show here that these multigenic families are extended and functionally related in wood-decaying fungi. Furthermore, we postulate that these rapidly evolving multigenic families could reflect the adaptation of these fungi to the diversity of their substrate and provide keys to understand their ecology. This is of particular importance for white biotechnology, this xenome being a putative target for improving degradation properties of these fungi in biomass valorization purposes.
    Full-text · Article · Jan 2013 · Microbial Biotechnology
  • Source
    • "In agreement with a role for LrgAB in oxidative stress resistance, several LytST-regulated genes identified in this study have also been implicated in bacterial oxidative stress responses. Upregulated potential oxidative stress genes include yghU, a putative anti-oxidant enzyme [50], tpx, a predicted thiol peroxidase [55], and recJ, a single-stranded DNA exonuclease protein that facilitates DNA repair in response to oxidative stress [51]. Conversely, several genes belonging to the TnSMu2 gene cluster (SMU.1334c "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background The S. mutans LrgA/B holin-like proteins have been shown to affect biofilm formation and oxidative stress tolerance, and are regulated by oxygenation, glucose levels, and by the LytST two-component system. In this study, we sought to determine if LytST was involved in regulating lrgAB expression in response to glucose and oxygenation in S. mutans. Results Real-time PCR revealed that growth phase-dependent regulation of lrgAB expression in response to glucose metabolism is mediated by LytST under low-oxygen conditions. However, the effect of LytST on lrgAB expression was less pronounced when cells were grown with aeration. RNA expression profiles in the wild-type and lytS mutant strains were compared using microarrays in early exponential and late exponential phase cells. The expression of 40 and 136 genes in early-exponential and late exponential phase, respectively, was altered in the lytS mutant. Although expression of comYB, encoding a DNA binding-uptake protein, was substantially increased in the lytS mutant, this did not translate to an effect on competence. However, a lrgA mutant displayed a substantial decrease in transformation efficiency, suggestive of a previously-unknown link between LrgA and S. mutans competence development. Finally, increased expression of genes encoding antioxidant and DNA recombination/repair enzymes was observed in the lytS mutant, suggesting that the mutant may be subjected to increased oxidative stress during normal growth. Although the intracellular levels of reaction oxygen species (ROS) appeared similar between wild-type and lytS mutant strains after overnight growth, challenge of these strains with hydrogen peroxide (H2O2) resulted in increased intracellular ROS in the lytS mutant. Conclusions Overall, these results: (1) Reinforce the importance of LytST in governing lrgAB expression in response to glucose and oxygen, (2) Define a new role for LytST in global gene regulation and resistance to H2O2, and (3) Uncover a potential link between LrgAB and competence development in S. mutans.
    Full-text · Article · Sep 2012 · BMC Microbiology
Show more