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  • 1.
    Andresen, Liis
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Tenson, Tanel
    Hauryliuk, Vasili
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia.
    Cationic bactericidal peptide 1018 does not specifically target the stringent response alarmone (p)ppGpp2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 36549Article in journal (Refereed)
    Abstract [en]

    The bacterial stringent response is a key regulator of bacterial virulence, biofilm formation and antibiotic tolerance, and is a promising target for the development of new antibacterial compounds. The intracellular nucleotide (p)ppGpp acts as a messenger orchestrating the stringent response. A synthetic peptide 1018 was recently proposed to specifically disrupt biofilms by inhibiting the stringent response via direct interaction with (p) ppGpp (de la Fuente-Nunez et al. (2014) PLoS Pathogens). We have interrogated the specificity of the proposed molecular mechanism. When inhibition of Pseudomonas aeruginosa planktonic and biofilm growth is tested simultaneously in the same assay, peptides 1018 and the control peptide 8101 generated by an inversion of the amino acid sequence of 1018 are equally potent, and, importantly, do not display a preferential activity against biofilm. 1018 inhibits planktonic growth of Escherichia coli equally efficiently either when the alleged target, (p) ppGpp, is essential (MOPS media lacking amino acid L-valine), or dispensable for growth (MOPS media supplemented with L-valine). Genetic disruption of the genes relA and spoT responsible for (p) ppGpp synthesis moderately sensitizes-rather than protects-E. coli to 1018. We suggest that the antimicrobial activity of 1018 does not rely on specific recognition of the stringent response messenger (p) ppGpp.

  • 2.
    Andresen, Liis
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Varik, Vallo
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia.
    Tozawa, Yuzuru
    Jimmy, Steffi
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Lindberg, Stina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tenson, Tanel
    Hauryliuk, Vasili
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia.
    Auxotrophy-based High Throughput Screening assay for the identification of Bacillus subtilis stringent response inhibitors2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 35824Article in journal (Refereed)
    Abstract [en]

    The stringent response is a central adaptation mechanism that allows bacteria to adjust their growth and metabolism according to environmental conditions. The functionality of the stringent response is crucial for bacterial virulence, survival during host invasion as well as antibiotic resistance and tolerance. Therefore, specific inhibitors of the stringent response hold great promise as molecular tools for disarming and pacifying bacterial pathogens. By taking advantage of the valine amino acid auxotrophy of the Bacillus subtilis stringent response-deficient strain, we have set up a High Throughput Screening assay for the identification of stringent response inhibitors. By screening 17,500 compounds, we have identified a novel class of antibacterials based on the 4-(6-(phenoxy) alkyl)-3,5-dimethyl-1H-pyrazole core. Detailed characterization of the hit compounds as well as two previously identified promising stringent response inhibitors-a ppGpp-mimic nucleotide Relacin and cationic peptide 1018 - showed that neither of the compounds is sufficiently specific, thus motivating future application of our screening assay to larger and more diverse molecular libraries.

  • 3. Beljantseva, Jelena
    et al.
    Kudrin, Pavel
    Andresen, Liis
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Shingler, Vicky
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Atkinson, Gemma C.
    Tenson, Tanel
    Hauryliuk, Vasili
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Institute of Technology, University of Tartu, 50411 Tartu, Estonia.
    Negative allosteric regulation of Enterococcus faecalis small alarmone synthetase RelQ by single-stranded RNA2017In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 114, no 14, p. 3726-3731Article in journal (Refereed)
    Abstract [en]

    The alarmone nucleotides guanosine pentaphosphate (pppGpp) and tetraphosphate (ppGpp), collectively referred to as (p)ppGpp, are key regulators of bacterial growth, stress adaptation, pathogenicity, and antibiotic tolerance. We show that the tetrameric small alarmone synthetase (SAS) RelQ from the Gram-positive pathogen Enterococcus faecalis is a sequence-specific RNA-binding protein. RelQ's enzymatic and RNA binding activities are subject to intricate allosteric regulation. (p)ppGpp synthesis is potently inhibited by the binding of single-stranded RNA. Conversely, RelQ's enzymatic activity destabilizes the RelQ: RNA complex. pppGpp, an allosteric activator of the enzyme, counteracts the effect of RNA. Tetramerization of RelQ is essential for this regulatory mechanism, because both RNA binding and enzymatic activity are abolished by deletion of the SAS-specific C-terminal helix 5 alpha. The interplay of pppGpp binding, (p)ppGpp synthesis, and RNA binding unites two archetypal regulatory paradigms within a single protein. The mechanism is likely a prevalent but previously unappreciated regulatory switch used by the widely distributed bacterial SAS enzymes.

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