The rhodanese RhdA helps Azotobacter vinelandii in maintaining cellular redox balance

Abstract

The tandem domain rhodanese-homology protein RhdA of Azotobacter vinelandii shows an active-site loop structure that confers structural peculiarity in the environment of its catalytic cysteine residue. The in vivo effects of the lack of RhdA were investigated using an A. vinelandii mutant strain (MV474) in which the rhdA gene was disrupted by deletion. Here, by combining analytical measurements and transcript profiles, we show that deletion of the rhdA gene generates an oxidative stress condition to which A. vinelandii responds by activating defensive mechanisms. In conditions of growth in the presence of the superoxide generator phenazine methosulfate, a stressor-dependent induction of rhdA gene expression was observed, thus highlighting that RhdA is important for A. vinelandii to sustain oxidative stress. The potential of RhdA to buffer general levels of oxidants in A. vinelandii cells via redox reactions involving its cysteine thiol is discussed.

Roles of Sulfur Metabolism and Rhodanese in Detoxification and Anti-Oxidative Stress Functions in the Liver: Responses to Radiation Exposure

“…Although rhodanese seems to have anti-oxidative functions in mammals, its original function is suggested by its participation in anti-oxidative regulation of intracellular homeostasis in the bacterium Azotobacter vinelandii . Deletion of Rhodanese-like protein (RhdA) produces oxidative imbalance in the strain [21,22]. Rhodanese or rhodanese-like proteins are present in all domains of life [18].…”

Rhodanese Functions as Sulfur Supplier for Key Enzymes in Sulfur Energy Metabolism

“…Despite numerous studies, the physiological role of rhodaneses as well as their physiological substrates remain unclear and are still widely debated. It has been proposed that they accomplish essential cell functions as they may be involved in the maintenance of redox homeostasis (20), in the elimination of toxic cyanide (21), and in the biosynthesis of several other cellular metabolites such as vitamins, enzymes, and cofactors that include a step of sulfur transfer (22)(23)(24)(25).…”

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

“…The internal oxidative problem and the ROS accumulation in A. vinelandii RhdA-null strain (MV474) previously demonstrated [14], [15], could trigger modifications of cellular components. Considering that peroxidation of lipids is one of the important intermediary events in free radical-induced cellular damage [35], we compared the content of lipid hydroperoxides (LHPOs) in A. vinelandii wild-type and MV474 strains.…”

“…The growths in gluconate as carbon source led to more marked effect than the growths in sucrose for which no significant difference is shown when data of LHPO amount are normalised on protein amount. It seems that the defensive mechanisms [15], [36] activated in the MV474 strain, are not adequate to counteract cellular damage in the absence of RhdA in A. vinelandii .…”

“…In the present work, the effects of the oxidative imbalance generated by the absence of RhdA in A. vinelandii were further defined, and, starting from the evidence that in the MV474 RhdA-null mutant strain the level of glutathione disulfide (GSSG) was higher with respect to that measured in the wild-type strain [15], we investigated a possible link between RhdA and homeostasis of reduced glutathione (GSH). We found that RhdA was able to bind in vitro GSH and to a lesser extent GSSG.…”