Glutathione Transferases of Phanerochaete chrysosporium

Abstract

The white rot fungus Phanerochaete chrysosporium, a saprophytic basidiomycete, possesses a large number of cytosolic glutathione transferases, eight of them showing similarity to the Omega class. PcGSTO1 (subclass I, the bacterial homologs of which were recently proposed, based on their enzymatic function, to constitute a new class of glutathione transferase named S-glutathionyl-(chloro)hydroquinone reductases) and PcGSTO3 (subclass II related to mammalian homologs) have been investigated in this study. Biochemical investigations demonstrate that both enzymes are able to catalyze deglutathionylation reactions thanks to the presence of a catalytic cysteinyl residue. This reaction leads to the formation of a disulfide bridge between the conserved cysteine and the removed glutathione from their substrate. The substrate specificity of each isoform differs. In particular PcGSTO1, in contrast to PcGSTO3, was found to catalyze deglutathionylation of S-glutathionyl-p-hydroquinone substrates. The three-dimensional structure of PcGSTO1 presented here confirms the hypothesis that it belongs not only to a new biological class but also to a new structural class that we propose to name GST xi. Indeed, it shows specific features, the most striking ones being a new dimerization mode and a catalytic site that is buried due to the presence of long loops and that contains the catalytic cysteine.

Structural Insights into Omega-Class Glutathione Transferases: A Snapshot of Enzyme Reduction and Identification of a Non-Catalytic Ligandin Site

“…These include Bombyx mori GSTO3-3 [27], Sphingobium sp. SYK-6 LigG [28], Phanerochaete chrysosporium GSTO3-3 [29] and Phanerochaete chrysosporium GSTFuA [30]. While regions in the Bombyx mori GSTO3-3 and Sphingobium sp.…”

Structural and enzymatic insights into Lambda glutathione transferases from Populus trichocarpa, monomeric enzymes constituting an early divergent class specific to terrestrial plants

“…We investigated the ability of recombinant Pt-GSTLs to catalyse the deglutathionylation of MEN-SG, TETRA-SG and PAP-SG, three substrates used for the characterization of several human and fungal GSTOs and fungal GHRs [8,46,55], whose structures are close to GSTLs. After synthesis and purification of each substrate, Pt-GSTL activities were monitored by analytical HPLC in the presence of GSH.…”

“…As GHRs and GSTOs, GSTLs have an unusually long N-terminal extension [8,51]. Although the sequences of Pt-GSTL2 and Pt-GSTL3 are highly homologous and both proteins were expressed and purified to homogeneity, no crystals were obtained for Pt-GSTL2.…”

“…Many successive GST classifications were proposed on the basis of criteria such as the sequence similarities, the nature of the catalytic residue and the biochemical properties [1,2]. Moreover, an additional class containing orthologues of bacterial and fungal GHRs (glutathionyl hydroquinone reductases) exists in plants [7][8][9]. In plants, in silico analyses of Populus trichocarpa (poplar), Arabidopsis thaliana, Oryza sativa (rice), Pinus taeda (loblolly pine), Hordeum vulgare (barley), Selaginella moellendorffii and Physcomitrella patens genomes allowed the identification of 81, 57, 83, 56, 84, 65 and 37 GSTs respectively [4][5][6].…”

The still mysterious roles of cysteine-containing glutathione transferases in plants

“…This capacity usually originates from the replacement of the catalytic serine or tyrosine residues in the active site motif by a cysteinyl residue as demonstrated for mammalian, insect and fungal Omega GSTs (GSTOs) (Board et al, 2000; Kim et al, 2006; Yamamoto et al, 2009; Meux et al, 2013), for plant Lambda GSTs (GSTLs) (Dixon and Edwards, 2010b; Lallement et al, 2014) and for bacterial and fungal glutathionyl hydroquinone reductases (GHRs) (Xun et al, 2010; Meux et al, 2011). However, the physiological functions of these enzymes have rarely been elucidated.…”