Involvement of the Azotobacter vinelandii Rhodanese-Like Protein RhdA in the Glutathione Regeneration Pathway

Abstract

The phenotypic features of the Azotobacter vinelandii RhdA mutant MV474 (in which the rhdA gene was deleted) indicated that defects in antioxidant systems in this organism were related to the expression of the tandem-domain rhodanese RhdA. In this work, further insights on the effects of the oxidative imbalance generated by the absence of RhdA (e.g. increased levels of lipid hydroperoxides) are provided. Starting from the evidence that glutathione was depleted in MV474, and using both in silico and in vitro approaches, here we studied the interaction of wild-type RhdA and Cys230Ala site-directed RhdA mutant with glutathione species. We found that RhdA was able to bind in vitro reduced glutathione (GSH) and that RhdA-Cys230 residue was mandatory for the complex formation. RhdA catalyzed glutathione-disulfide formation in the presence of a system generating the glutathione thiyl radical (GS•, an oxidized form of GSH), thereby facilitating GSH regeneration. This reaction was negligible when the Cys230Ala RhdA mutant was used. The efficiency of RhdA as catalyst in GS•-scavenging activity is discussed on the basis of the measured parameters of both interaction with glutathione species and kinetic studies.

The Oxidative Stress Network of Mycobacterium tuberculosis Reveals Coordination between Radical Detoxification Systems

“…However, TST-like enzymes play diverse roles, and can also act as thiol oxidoreductases (Nandi et al, 2000). In particular, their ability to regenerate glutathione thiyl radicals has been proposed to explain the oxidative stress sensitivity of A. vinelandii TST mutants (Remelli et al, 2012). The possible roles for Rv3005c and SseA in thiol redox reactions, and their physical and genetic interactions with SodA led us to hypothesize that this three-protein complex might coordinate multiple enzymatic functions necessary for oxidative stress resistance during Mtb infection.…”

“…In mycobacteria, this promiscuity may be advantageous, as alternative thiol redox buffering systems such as those using ergothionine have been described (Kumar et al, 2011). The requirement for SodA in the MRC is likely due to its ability to detoxify radicals that are known to be generated during the SseA reaction (Remelli et al, 2012). Thus, the physical association between SOD and thiol oxidoreductase activities provides a biochemical explanation for the unexpected diamide sensitivity of SodA-deficient mutants.…”

Homozygous Truncating Variants in TBC1D23 Cause Pontocerebellar Hypoplasia and Alter Cortical Development

“…The function of this domain is still elusive, but thiosulfate sulfutransferase activity with cyanide detoxification has been reported. 29,30 Until recently no substrates were known for TBC1D23. 20 Interestingly, TBC1D23 is a central partner of an interacting network of proteins implicating WDR62, STK11, UBC, PRKAR2B, TBC1D8, KIAA1033, and VPS26A.…”

Sulfurtransferase and thioredoxin specifically interact as demonstrated by bimolecular fluorescence complementation analysis and biochemical tests

“…Comparison with structurally related proteins shows that Trx shares a mechanism with glutaredoxin and glutathione transferase for correctly positioning substrate cysteine residues at the catalytic groups but possesses a unique structural element that allows recognition of protein disulfides [20] . Several non-Trx interaction partners of Strs have been suggested [35] . Probably other molecular mechanisms are responsible for the specificity.…”