CGFS-Type Monothiol Glutaredoxins from the Cyanobacterium Synechocystis PCC6803 and Other Evolutionary Distant Model Organisms Possess a Glutathione-Ligated [2Fe-2S] Cluster

Abstract

When produced in Escherichia coli, the CGFS-type monothiol Grxs from this organism (EcGrx4p) and the model cyanobacterium Synechocystis (SyGrx3p) exist as a dimeric iron-sulfur containing holoprotein or as a monomeric apoprotein in solution. Spectroscopic and site-directed mutagenesis analyses show that the SyGrx3 holoprotein contains a subunit-bridging [2Fe-2S] cluster that is ligated by the catalytic cysteine located in the CGFS motif of each monomer and the cysteines of two molecules of glutathione. The biochemical characterization of several monothiol Grxs from the cyanobacteria Gloeobacter violaceus (GvGrx3p) and Thermosynechococcus elongatus (TeGrx3p), the yeast Saccharomyces cerevisiae (ScGrx3p, ScGrx4p, and ScGrx5p), the plant Arabidopsis thaliana (AtGrx5p), and human (HsGrx5p) indicate that the incorporation of a GSH-ligated [2Fe-2S] center is a common feature of prokaryotic and eukaryotic CGFS-active site monothiol Grxs. In light of these results, the involvement of these enzymes in the sensing of iron and/or the biogenesis and transfer of Fe-S cluster is discussed.

Glutaredoxin GRXS17 Associates with the Cytosolic Iron-Sulfur Cluster Assembly Pathway

“…The yeast GRX proteins Grx3/4 and the mammalian ortholog GRX3/PKC-interacting cousin of TRX (PICOT) have been associated with the CIA pathway and contain themselves [2Fe-2S] clusters (Picciocchi et al, 2007;Haunhorst et al, 2010). Deletion of Grx3/4 in yeast leads to defects in cytosolic and mitochondrial Fe-S assembly, deregulation of iron homeostasis, and defects in proteins containing di-iron centers (Mühlenhoff et al, 2010).…”

Mono- and Dithiol Glutaredoxins in the Trypanothione-Based Redox Metabolism of Pathogenic Trypanosomes

“…As reported for several ISC-glutaredoxin complexes (6,25,40,42,43,54,67,75), most probably two GSH molecules act as the low molecular mass ligands of the ISC in the holo-form of the trypanosomal proteins extracted from E. coli. In vitro reconstitution of the iron-sulfur proteins in the presence of Gsp or T(SH) 2 revealed that these parasite specific thiols can easily substitute for GSH as the nonprotein ligand(s).…”

“…Except for yeast Grx6 and Grx7 (59,60), most 1-C-Grxs lack or have negligible classical disulfide reductase activity (18,26,27,43,69,82). Instead, the capability to coordinate ISCs appears to be a common feature for 1-C-Grxs (16,40,42,43,54,67,89) with yeast Grx7 being, so far, the only known exception (59,60). The latter feature determines an evolutionary conserved and indispensable role of 1-C-Grxs in the biogenesis and assembly of iron-sulfur proteins (11,61) and other cell-specific regulatory functions such as the (in)activation of nuclear transcription factors (35,62,86).…”

“…Strikingly, the dithiol T(SH) 2 was capable to ligate the chromophor also to the monomeric form of 2-C-Grx1 which probably represents an intermediate during formation of the holo-protein (12, 55a). A cysteine in the first position and the absence of a proline in the second position of the active site motif, as well as the noncovalent binding of GSH are conserved features among glutaredoxins capable of coordinating an ISC (6,25,40,42,43,54,67,75). For cluster coordination, T. brucei 1-C-Grx1 also relies on its active site cysteine but the protein is not definite with respect to the nature of the thiol ligand and the mechanism of ISC binding (55a).…”

Proteomic analysis of post translational modifications in cyanobacteria

“…Recently glutathionylation was reported to regulate the activity of two proteins from Synechocystis 6803 [88,89]. Synechocystis 6803 possesses only one monothiol [90] and two dithiol glutaredoxins (Grxs), which have been shown to specifically interact with various protein partners resistant to toxic metals and various other stresses [88,[91][92][93]. In addition, several targets of one dithiol Grx (Ssr2061) from Synechocystis have been identified by proteomic methods [94].…”