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- Lagunas-Rangel, Francisco Alejandro, et al.
(författare)
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Sirtuin GdSir2.4 participates in the regulation of rRNA transcription in the Giardia duodenalis parasite
- 2021
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 115:5, s. 1039-1053
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Tidskriftsartikel (refereegranskat)abstract
- Giardia duodenalis is a parasite of great medical interest due to the number of infections it causes worldwide each year. Although research on epigenetic mechanisms in this protist has only begun recently, epigenetic regulation has already been shown to have important roles in encystation, antigenic variation, and resistance to antibiotics in Giardia. In this work, we show that a Giardia ortholog of Sir2, GdSir2.4, is involved in the silencing of rRNA expression. Our results demonstrate that GdSir2.4 localizes to the nucleolus, and its binding to the intergenic spacer region of the rDNA is associated with the deacetylation of the chromatin in this region. Given the importance of the regulation of rRNA expression to maintain adequate levels of ribosomes and genomic stability within the cells, GdSir2.4 can be considered a target to create new therapeutic agents against this parasite.
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- Mandin, Pierre, et al.
(författare)
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Feeling the heat at the millennium : thermosensors playing with fire
- 2020
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 113:3, s. 588-592
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Forskningsöversikt (refereegranskat)abstract
- An outstanding question regards the ability of organisms to sense their environments and respond in a suitable way. Pathogenic bacteria in particular exploit host-temperature sensing as a cue for triggering virulence gene expression. This micro-review does not attempt to fully cover the field of bacterial thermosensors and in detail describe each identified case. Instead, the review focus on the time-period at the end of the 1990's and beginning of the 2000's when several key discoveries were made, identifying protein, DNA and RNA as potential thermosensors controlling gene expression in several different bacterial pathogens in general and on the prfA thermosensor of Listeria monocytogenes in particular.
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- Osaka, Natsuki, et al.
(författare)
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Novel (p)ppGpp(0) suppressor mutations reveal an unexpected link between methionine catabolism and GTP synthesis in Bacillus subtilis
- 2020
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 113:6, s. 1155-1169
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Tidskriftsartikel (refereegranskat)abstract
- In bacteria, guanosine (penta)tetra-phosphate ([p]ppGpp) is essential for controlling intracellular metabolism that is needed to adapt to environmental changes, such as amino acid starvation. The (p)ppGpp(0) strain of Bacillus subtilis, which lacks (p)ppGpp synthetase, is unable to form colonies on minimal medium. Here, we found suppressor mutations in the (p)ppGpp(0) strain, in the purine nucleotide biosynthesis genes, prs, purF and rpoB/C, which encode RNA polymerase core enzymes. In comparing our work with prior studies of ppGpp(0) suppressors, we discovered that methionine addition masks the suppression on minimal medium, especially of rpoB/C mutations. Furthermore, methionine addition increases intracellular GTP in rpoB suppressor and this effect is decreased by inhibiting GTP biosynthesis, indicating that methionine addition activated GTP biosynthesis and inhibited growth under amino acid starvation conditions in (p)ppGpp(0) backgrounds. Furthermore, we propose that the increase in intracellular GTP levels induced by methionine is due to methionine derivatives that increase the activity of the de novo GTP biosynthesis enzyme, GuaB. Our study sheds light on the potential relationship between GTP homeostasis and methionine metabolism, which may be the key to adapting to environmental changes.
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- Palmer, Tracy, et al.
(författare)
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A holin/peptidoglycan hydrolase-dependent protein secretion system
- 2021
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 115:3, s. 345-355
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Tidskriftsartikel (refereegranskat)abstract
- Gram-negative bacteria have evolved numerous pathways to secrete proteins across their complex cell envelopes. Here, we describe a protein secretion system which uses a holin membrane protein in tandem with a cell wall editing enzyme to mediate the secretion of substrate proteins from the periplasm to the cell exterior. The identity of the cell wall editing enzymes employed was found to vary across biological systems. For instance, the chitinase secretion pathway of Serratia marcescens uses an endopeptidase to facilitate secretion, whereas the secretion of Typhoid toxin in Salmonella enterica serovar Typhi relies on a muramidase. Various families of holins are also predicted to be involved. Genomic analysis indicates that this pathway is conserved and implicated in the secretion of hydrolytic enzymes and toxins for a range of bacteria. The pairing of holins from different families with various types of peptidoglycan hydrolases suggests that this secretion pathway evolved multiple times. We suggest that the complementary bodies of evidence presented is sufficient to propose that the pathway be named the Type 10 Secretion System (TXSS). Potential mechanisms for secretion across the outer membrane are discussed.
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- Passot, Fanny M., et al.
(författare)
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Protein phosphatase SppA regulates apical growth and dephosphorylates cell polarity determinant DivIVA in Streptomyces coelicolor
- 2021
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958.
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Tidskriftsartikel (refereegranskat)abstract
- Members of the Actinobacteria, including mycobacteria and streptomycetes, exhibit a distinctive mode of polar growth, with cell wall synthesis occurring in zones at cell poles and directed by the essential cell polarity determinant DivIVA. Streptomyces coelicolor modulates polar growth via the Ser/Thr protein kinase AfsK, which phosphorylates DivIVA. Here, we show that the phosphoprotein phosphatase SppA has strong effects on polar growth and cell shape and that it reverses the AfsK-mediated phosphorylation of DivIVA. SppA affects hyphal branching and the rate of tip extension. The sppA mutant hyphae also exhibit a high frequency of spontaneous growth arrests, indicating problems with maintenance of tip extension. The phenotypic effects are partially suppressed in an afsK sppA double mutant, indicating that AfsK and SppA to some extent share target proteins. Strains with a nonphosphorylatable mutant DivIVA confirm that the effect of afsK on hyphal branching during normal growth is mediated by DivIVA phosphorylation. However, the phenotypic effects of sppA deletion are independent of DivIVA phosphorylation and must be mediated via other substrates. This study adds a PPP-family protein phosphatase to the proteins involved in the control of polar growth and cell shape determination in S. coelicolor.
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- Segawa, Takaya, et al.
(författare)
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Two ABC transport systems carry out peptide uptake in Enterococcus faecalis : Their roles in growth and in uptake of sex pheromones
- 2021
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 116:2, s. 459-469
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Tidskriftsartikel (refereegranskat)abstract
- Enterococcal pheromone-inducible plasmids encode a predicted OppA-family secreted lipoprotein. In the case of plasmid pCF10, the protein is PrgZ, which enhances the mating response to cCF10 pheromone. OppA proteins generally function with associated OppBCDF ABC transporters to import peptides. In this study, we analyzed the potential interactions of PrgZ with two host-encoded Opp transporters using two pheromone-inducible fluorescent reporter constructs. Based on our results, we propose renaming these loci opp1 (OG1RF_10634-10639) and opp2 (OG1RF_12366-12370). We also examined the ability of the Opp1 and Opp2 systems to mediate import in the absence of PrgZ. Cells expressing PrgZ were able to import pheromone if either opp1 or opp2 was functional, but not if both opp loci were disrupted. In the absence of PrgZ, pheromone import was dependent on a functional opp2 system, including opp2A. Comparative structural analysis of the peptide-binding pockets of PrgZ, Opp1A, Opp2A, and the related Lactococcus lactis OppA protein, suggested that the robust pheromone-binding ability of PrgZ relates to a nearly optimal fit of the hydrophobic peptide, whereas binding ability of Opp2A likely results from a more open, promiscuous peptide-binding pocket similar to L. lactis OppA.
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- von Wachenfeldt, Claes, et al.
(författare)
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YtkA (CtaK) and YozB (CtaM) function in the biogenesis of cytochrome c oxidase in Bacillus subtilis
- 2021
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Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 116:1, s. 184-199
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Tidskriftsartikel (refereegranskat)abstract
- Cytochrome c oxidase in the respiratory chain of bacteria and mitochondria couples the reduction of molecular oxygen to form water with the generation of a transmembrane proton gradient. Bacillus subtilis has two heme A-containing heme–copper oxidases: the menaquinol oxidase cytochrome aa3 and the cytochrome c oxidase cytochrome caa3. By screening three collections of mutants for defective cytochrome c oxidase, we found the genes for two, new membrane-bound assembly factors in B. subtilis: ytkA and yozB (renamed ctaK and ctaM, respectively). CtaK is a lipoprotein without sequence similarity to any protein of known function. We show that CtaK functions together with Sco1 (YpmQ) in a pathway, leading to the assembly of the CuA center in cytochrome caa3 and seems to be a functional analogue to proteins of the periplasmic CuA chaperone family (PCuAC). CtaM is required for the activity of both cytochrome caa3 and cytochrome aa3 and dispensable for the insertion of heme A into these oxidases. The orthologous Bacillus anthracis protein and the distantly related Staphylococcus aureus CtaM complemented CtaM deficiency in B. subtilis, establishing a common function of CtaM in these bacteria. As the overall result of our work, 12 different proteins are known to function in the biosynthesis of cytochrome c oxidase in B. subtilis.
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