Interactions of glutaredoxins, ribonucleotide reductase, and components of the DNA replication system of
            <i>Escherichia coli</i>

Ortenberg, Ron; Gon, Stéphanie; Porat, Amir; Beckwith, Jon

doi:10.1073/pnas.0401965101

Cited by 59 publications

(65 citation statements)

References 31 publications

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“…Furthermore, subtle differences in the ribonucleotide reductase binding platform on the SSH and the extension of the HSL suggest possible routes for rational speciesselective drug design. For example, mutation of the SSH in E. coli GLXR3 allows it to thrive even in the inviable background containing gene knockouts for thioredoxin 1, thioredoxin 2 and GLXR1 (Ortenberg et al, 2004). This mutation of Met43 to valine, isoleucine or leucine in the SSH seems to exert the restoration of its viability via enhanced interactions with ribonucleotide reductase, consistent with studies on GLXR bound to model peptides that point to a direct interaction with the SSH (Berardi & Bushweller, 1999).…”

Section: Discussionsupporting

confidence: 71%

Comparative analysis of glutaredoxin domains from bacterial opportunistic pathogens

et al. 2011

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PDB References: BrabA.00079.a, 2khp; BaheA.00334.a, 2klx.Glutaredoxin proteins (GLXRs) are essential components of the glutathione system that reductively detoxify substances such as arsenic and peroxides and are important in the synthesis of DNA via ribonucleotide reductases. NMR solution structures of glutaredoxin domains from two Gram-negative opportunistic pathogens, Brucella melitensis and Bartonella henselae, are presented. These domains lack the N-terminal helix that is frequently present in eukaryotic GLXRs. The conserved active-site cysteines adopt canonical proline/tyrosinestabilized geometries. A difference in the angle of -helix 2 relative to the -sheet surface and the presence of an extended loop in the human sequence suggests potential regulatory regions and/or protein-protein interaction motifs. This observation is consistent with mutations in this region that suppress defects in GLXR-ribonucleotide reductase interactions. These differences between the human and bacterial forms are adjacent to the dithiol active site and may permit species-selective drug design.

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Section: Discussionsupporting

confidence: 71%

Comparative analysis of glutaredoxin domains from bacterial opportunistic pathogens

et al. 2011

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“…In other organisms, such as E. coli, different components of the cellular redox systems show some specificity yet there is significant redundancy as well (6,29,34,35,46,53). The glutathione/glutaredoxin and TrxB/Trx systems share the ability to reduce many overlapping cytoplasmic substrates, including RNR (2,23).…”

Section: Discussionmentioning

confidence: 99%

Thioredoxins in Redox Maintenance and Survival during Oxidative Stress ofBacteroides fragilis

et al. 2009

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The anaerobe Bacteroides fragilis is a gram-negative, opportunistic pathogen that is highly aerotolerant and can persist in aerobic environments for extended periods. In this study, the six B. fragilis thioredoxins (Trxs) were investigated to determine their role during oxidative stress. Phylogenetic analyses of Trx protein sequences indicated that four of the six Trxs (TrxA, TrxC, TrxD, and TrxF) belong to the M-type Trx class but were associated with two different M-type lineages. TrxE and TrxG were most closely associated to Y-type Trxs found primarily in cyanobacteria. Single and multiple trx gene deletions were generated to determine functional differences between the Trxs. The trxA gene was essential, but no anaerobic growth defects were observed for any other single trx deletion or for the ⌬trxC ⌬trxD::cfxA ⌬trxE ⌬trxF ⌬trxG quintuple mutant. Regulation of the trx genes was linked to the oxidative stress response, and all were induced by aerobic conditions. The ⌬trxC ⌬trxE ⌬trxF ⌬trxG and the ⌬trxC ⌬trxD::cfxA ⌬trxE ⌬trxF ⌬trxG multiple deletion strains were impaired during growth in oxidized media, but single trx gene mutants did not have a phenotype in this assay. TrxD was protective during exposure to the thiol oxidant diamide, and expression of trxD was induced by diamide. Diamide-induced expression of trxC, trxE, and trxF increased significantly in a trxD mutant strain, suggesting that there is some capacity for compensation in this complex Trx system. These data provide insight into the role of individual Trxs in the B. fragilis oxidative stress response.

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“…For example, the two E. coli thioredoxins TrxA and TrxC and the glutaredoxin GrxA are known to be required for cellular DNA synthesis by acting as electron donors for the essential enzyme ribonucleotide reductase (14,30). The other physiological functions that are accomplished by reduced thioredoxins include protein disulfide reduction, sulfur assimilation, detoxification of reactive oxygen species, protein repair, and redox regulation of enzymes and transcription factors (2,6,31).…”

mentioning

confidence: 99%

Functional Studies of Multiple Thioredoxins from Mycobacterium tuberculosis

Akif¹,

Khare

Tyagi

et al. 2008

J Bacteriol

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Cytoplasmic protein reduction via generalized thiol/disulfide exchange reactions and maintenance of cellular redox homeostasis is mediated by the thioredoxin superfamily of proteins. Here, we describe the characterization of the thioredoxin system from Mycobacterium tuberculosis, whose genome bears the potential to encode three putative thioredoxins from the open reading frames designated trxA Mtb , trxB Mtb , and trxC Mtb . We show that all three thioredoxins, overproduced in Escherichia coli, are able to reduce insulin, a model substrate, in the presence of dithiothreitol. However, we observe that thioredoxin reductase is not capable of reducing TrxA Mtb in an NADPH-dependent manner, indicating that only TrxB Mtb and TrxC Mtb are the biologically active disulfide reductases. The absence of detectable mRNA transcripts of trxA Mtb observed when M. tuberculosis strain H37Rv was cultivated under different growth conditions suggests that trxA Mtb expression may be cryptic. The measured redox potentials of TrxB Mtb and TrxC Mtb (؊262 ؎ 2 mV and ؊269 ؎ 2 mV, respectively) render these proteins somewhat more oxidizing than E. coli thioredoxin 1 (TrxA). In E. coli strains lacking components of cytoplasmic protein reduction pathways, heterologous expression of the mycobacterial thioredoxins was able to effectively substitute for their function.The cytoplasm in living cells is maintained in the reduced state by the activities of specialized enzyme systems comprising members of the oxidoreductase family that perform generalized protein reduction (2). In the well-studied example of Escherichia coli, the thioredoxin (Trx) system comprises two thioredoxins and thioredoxin reductase, while the glutaredoxin (Grx) system is composed of glutathione (GSH), three glutaredoxins, and GSH oxidoreductase. Trx, with an approximate mass of 12,000 Da, is found ubiquitously in nature. All thioredoxins share similar three-dimensional structures and possess a conserved WCXXC catalytic motif, buried within a protein fold known as the thioredoxin fold (27). Thioredoxins are able to cycle between the oxidized disulfide and the reduced dithiol forms. Oxidized Trx is in turn reduced by a flavoenzyme, thioredoxin reductase, via a redox-active cysteine pair and flavin adenine dinucleotide as a cofactor consuming cellular NADPH. Reduced Trx generated in this manner is thus poised for reducing disulfides of the target proteins in the cellular milieu (20).The NADPH-dependent disulfide reduction mechanism is required for a variety of physiological functions. For example, the two E. coli thioredoxins TrxA and TrxC and the glutaredoxin GrxA are known to be required for cellular DNA synthesis by acting as electron donors for the essential enzyme ribonucleotide reductase (14, 30). The other physiological functions that are accomplished by reduced thioredoxins include protein disulfide reduction, sulfur assimilation, detoxification of reactive oxygen species, protein repair, and redox regulation of enzymes and transcription factors (2, 6, 31). Apart from t...

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Interactions of glutaredoxins, ribonucleotide reductase, and components of the DNA replication system of Escherichia coli

Cited by 59 publications

References 31 publications

Comparative analysis of glutaredoxin domains from bacterial opportunistic pathogens

Comparative analysis of glutaredoxin domains from bacterial opportunistic pathogens

Thioredoxins in Redox Maintenance and Survival during Oxidative Stress ofBacteroides fragilis

Functional Studies of Multiple Thioredoxins from Mycobacterium tuberculosis

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