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| 2. |
- Gerdes, Kenn, et al.
(författare)
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RNA antitoxins
- 2007
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Ingår i: Current Opinion in Microbiology. - : Elsevier BV. - 1369-5274 .- 1879-0364. ; 10:2, s. 117-124
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Forskningsöversikt (refereegranskat)abstract
- Recent genomic analyses revealed a surprisingly large number of toxin–antitoxin loci in free-living prokaryotes. The antitoxins are proteins or antisense RNAs that counteract the toxins. Two antisense RNA-regulated toxin–antitoxin gene families, hok/sok and ldr, are unrelated sequence-wise but have strikingly similar properties at the level of gene and RNA organization. Recently, two SOS-induced toxins were found to be regulated by RNA antitoxins. One such toxin, SymE, exhibits similarity with MazE antitoxin and, surprisingly, inhibits translation. Thus, it is possible that an ancestral antitoxin gene evolved into the present toxin gene (symE) whose translation is repressed by an RNA antitoxin (SymR).
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| 3. |
- Hauryliuk, Vasili, 1980-, et al.
(författare)
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Recent functional insights into the role of (p)ppGpp in bacterial physiology
- 2015
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Ingår i: Nature Reviews Microbiology. - : Macmillan Publishers Ltd.. - 1740-1526 .- 1740-1534. ; 13:5, s. 298-309
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Forskningsöversikt (refereegranskat)abstract
- The alarmones guanosine tetraphosphate and guanosine pentaphosphate (collectively referred to as (p) ppGpp) are involved in regulating growth and several different stress responses in bacteria. In recent years, substantial progress has been made in our understanding of the molecular mechanisms of (p) ppGpp metabolism and (p) ppGpp-mediated regulation. In this Review, we summarize these recent insights, with a focus on the molecular mechanisms governing the activity of the RelA/SpoT homologue (RSH) proteins, which are key players that regulate the cellular levels of (p) ppGpp. We also discuss the structural basis of transcriptional regulation by (p) ppGpp and the role of (p) ppGpp in GTP metabolism and in the emergence of bacterial persisters.
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| 4. |
- Manav, Melek Cemre, et al.
(författare)
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The E. coli HicB Antitoxin Contains a Structurally Stable Helix-Turn-Helix DNA Binding Domain
- 2019
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Ingår i: Structure. - : Elsevier. - 0969-2126 .- 1878-4186. ; 27:11, s. 1675-
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Tidskriftsartikel (refereegranskat)abstract
- The E. coli hicAB type II toxin-antitoxin locus is unusual by being controlled by two promoters and by having the toxin encoded upstream of the antitoxin. HicA toxins contain a double-stranded RNA-binding fold and cleaves both mRNA and tmRNA in vivo, while HicB antitoxins contain a partial RNase H fold and either a helix-turn-helix (HTH) or ribbon-helix-helix domain. It is not known how an HTH DNA-binding domain affects higher-order structure for the HicAB modules. Here, we present crystal structures of the isolated E. coli HicB antitoxin and full-length HicAB complex showing that HicB forms a stable DNA-binding module and interacts in a canonical way with HicA despite the presence of an HTH-type DNA-binding domain. No major structural rearrangements take place upon binding of the toxin. Both structures expose well-ordered DNA-binding motifs allowing a model for DNA binding by the antitoxin to be generated.
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| 5. |
- Nielsen, Stine Vang, et al.
(författare)
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Serine-Threonine Kinases Encoded by Split hipA Homologs Inhibit Tryptophanyl-tRNA Synthetase
- 2019
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Ingår i: mBio. - : American Society for Microbiology. - 2161-2129 .- 2150-7511. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Type II toxin-antitoxin (TA) modules encode a stable toxin that inhibits cell growth and an unstable protein antitoxin that neutralizes the toxin by direct protein-protein contact. hipBA of Escherichia coli strain K-12 codes for HipA, a serinethreonine kinase that phosphorylates and inhibits glutamyl-tRNA synthetase. Induction of hipA inhibits charging of glutamyl-tRNA that, in turn, inhibits translation and induces RelA-dependent (p) ppGpp synthesis and multidrug tolerance. Here, we describe the discovery of a three-component TA gene family that encodes toxin HipT, which exhibits sequence similarity with the C-terminal part of HipA. A genetic screening revealed that trpS in high copy numbers suppresses HipT-mediated growth inhibition. We show that HipT of E. coli O127 is a kinase that phosphorylates tryptophanyl-tRNA synthetase in vitro at a conserved serine residue. Consistently, induction of hipT inhibits cell growth and stimulates production of (p) ppGpp. The gene immediately upstream from hipT, called hipS, encodes a small protein that exhibits sequence similarity with the N terminus of HipA. HipT kinase was neutralized by cognate HipS in vivo, whereas the third component, HipB, encoded by the first gene of the operon, did not counteract HipT kinase activity. However, HipB augmented the ability of HipS to neutralize HipT. Analysis of two additional hipBSThomologous modules showed that, indeed, HipS functions as an antitoxin in these cases also. Thus, hipBST constitutes a novel family of tricomponent TA modules where hipA has been split into two genes, hipS and hipT, that function as a novel type of TA pair.IMPORTANCE: Bacterial toxin-antitoxin (TA) modules confer multidrug tolerance (persistence) that may contribute to the recalcitrance of chronic and recurrent infections. The first high-persister gene identified was hipA of Escherichia coli strain K-12, which encodes a kinase that inhibits glutamyl-tRNA synthetase. The hipA gene encodes the toxin of the hipBA TA module, while hipB encodes an antitoxin that counteracts HipA. Here, we describe a novel, widespread TA gene family, hipBST, that encodes HipT, which exhibits sequence similarity with the C terminus of HipA. HipT is a kinase that phosphorylates tryptophanyl-tRNA synthetase and thereby inhibits translation and induces the stringent response. Thus, this new TA gene family may contribute to the survival and spread of bacterial pathogens.
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| 7. |
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| 8. |
- Sinha, Anurag Kumar, et al.
(författare)
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Fatty acid starvation activates RelA by depleting lysine precursor pyruvate
- 2019
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 112:4, s. 1339-1349
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Tidskriftsartikel (refereegranskat)abstract
- Bacteria undergoing nutrient starvation induce the ubiquitous stringent response, resulting in gross physiological changes that reprograms cell metabolism from fast to slow growth. The stringent response is mediated by the secondary messengers pppGpp and ppGpp collectively referred to as (p)ppGpp or 'alarmone'. In Escherichia coli, two paralogs, RelA and SpoT, synthesize (p)ppGpp. RelA is activated by amino acid starvation, whereas SpoT, which can also degrade (p)ppGpp, responds to fatty acid (FA), carbon and phosphate starvation. Here, we discover that FA starvation leads to rapid activation of RelA and reveal the underlying mechanism. We show that FA starvation leads to depletion of lysine that, in turn, leads to the accumulation of uncharged tRNA(Lys) and activation of RelA. SpoT was also activated by FA starvation but to a lower level and with a delayed kinetics. Next, we discovered that pyruvate, a precursor of lysine, is depleted by FA starvation. We also propose a mechanism that explains how FA starvation leads to pyruvate depletion. Together our results raise the possibility that RelA may be a major player under many starvation conditions previously thought to depend principally on SpoT. Interestingly, FA starvation provoked a similar to 100-fold increase in relA dependent ampicillin tolerance.
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