Rubrerythrin and Rubredoxin Oxidoreductase inDesulfovibrio vulgaris: a Novel Oxidative Stress Protection System

Abstract

Evidence is presented for an alternative to the superoxide dismutase (SOD)-catalase oxidative stress defense system in Desulfovibrio vulgaris (strain Hildenborough). This alternative system consists of the nonheme iron proteins, rubrerythrin (Rbr) and rubredoxin oxidoreductase (Rbo), the product of the rbo gene (also called desulfoferrodoxin). A ⌬rbo strain of D. vulgaris was found to be more sensitive to internal superoxide exposure than was the wild type. Unlike Rbo, expression of plasmid-borne Rbr failed to restore the aerobic growth of a SOD-deficient strain of Escherichia coli. Conversely, plasmid-borne expression of two different Rbrs from D. vulgaris increased the viability of a catalase-deficient strain of E. coli that had been exposed to hydrogen peroxide whereas Rbo actually decreased the viability. A previously undescribed D. vulgaris gene was found to encode a protein having 50% sequence identity to that of E. coli Fe-SOD. This gene also encoded an extended N-terminal sequence with high homologies to export signal peptides of periplasmic redox proteins. The SOD activity of D. vulgaris is not affected by the absence of Rbo and is concentrated in the periplasmic fraction of cell extracts. These results are consistent with a superoxide reductase rather than SOD activity of Rbo and with a peroxidase activity of Rbr. A joint role for Rbo and Rbr as a novel cytoplasmic oxidative stress protection system in D. vulgaris and other anaerobic microorganisms is proposed.

Kinetics studies of the superoxide-mediated electron transfer reactions between rubredoxin-type proteins and superoxide reductases

“…Inversely, aerotolerant organisms such as Dv and Dg are supposed to be exposed more briefly to oxygen and at much lower concentrations, as reflected in the lower k app values observed. In addition, Dv, which apparently possesses the lower SOR activity, was shown to express the gene for a periplasmic SOD [44]. These differences could reveal an extraordinary faculty of these organisms to deal with the oxidative stress, and we suggest that the efficiency of the superoxide-mediated electron transfer reactions may be related to an adaptation of the bacteria to environmental conditions.…”

“…In anaerobes, it is often observed that the genes encoding rubredoxin occur in the same operon or cluster as SORs, the gene for SOR usually being located some base pairs downstream of the gene-encoding rubredoxin [1,26,[43][44][45]. Moreover, a coordinated expression of the genes has also been described in some organisms, such as Dv and Desulfoarculus barsii [16,43,44].…”

Experimental design and environmental parameters affect Rhodospirillum rubrum S1H response to space flight

“…Differential gene expression that could be linked to oxidative stress putatively included the upregulation of the ferric uptake repressor fur (Rru_A3788), which links cellular iron status to oxidative stress by scavenging iron (Hantke, 2001;Imlay, 2003), and the downregulation of hfq, which negatively regulates the expression of Fur in E. coli (Vecerek et al, 2003). However, rubrerythrin involved in oxidative stress defense in anaerobic bacteria (Lehmann et al, 1996;Lumppio et al, 2001) was downregulated. Previous reports on the effect of low doses (in the range of 0.1 Gy of X-rays) on prokaryotes only focused on the induction of the adaptive response by means of SOS repair-related genes (Huang and Claycamp, 1993;Ewing, 1995;Basak, 1996) and Ewing (1995) predicted the threshold dose that just activates a physiological response (that is, SOS repair mechanism) in E. coli to be as low as 1 mGy.…”

A New Function of the Desulfovibrio vulgaris Hildenborough [Fe] Hydrogenase in the Protection against Oxidative Stress

“…As a matter of fact, cells contain a number of potential generators of superoxide anion, such as cytochrome, flavodoxin, and ferredoxin. Superoxide dismutase and catalase, which are enzymes well known to eliminate superoxide and hydrogen peroxide in aerobic organisms, have also been characterized in some Desulfovibrio species (17,18). In addition to these enzymes, a superoxide reductase (SOR) and a rubrerythrin, which has an NADH-dependent H 2 O 2 reductase activity, have also been found in sulfate-reducing bacteria (19 -22).…”