Browsing by Author "Tenson, Tanel"

Now showing 1 - 6 of 6

A hyperpromiscuous antitoxin protein domain for the neutralization of diverse toxin domains
(PNAS, 2022-02-04) kurata, Tatsuki; Saha, Chayan Kumar; Buttress, Jessica A.; Mets, Toomas; Brodiazhenko, Tetiana; Turnbull, Kathrin J; Awoyomi, Ololade F.; Oliveira, Sofia Raquel Alves; Jimmy, Steffi; Ernits, Karin; Delannoy, Maxence; Persson, Karina; Tenson, Tanel; Strahl, Henrik; Haurilyiuk, Vasili; Atkinson, Gemma C
Toxin–antitoxin (TA) gene pairs are ubiquitous in microbial chromosomal genomes and plasmids as well as temperate bacteriophages. They act as regulatory switches, with the toxin limiting the growth of bacteria and archaea by compromising diverse essential cellular targets and the antitoxin counteracting the toxic effect. To uncover previously uncharted TA diversity across microbes and bacteriophages, we analyzed the conservation of genomic neighborhoods using our computational tool FlaGs (for flanking genes), which allows high-throughput detection of TA-like operons. Focusing on the widespread but poorly experimentally characterized antitoxin domain DUF4065, our in silico analyses indicated that DUF4065-containing proteins serve as broadly distributed antitoxin components in putative TA-like operons with dozens of different toxic domains with multiple different folds. Given the versatility of DUF4065, we have named the domain Panacea (and proteins containing the domain, PanA) after the Greek goddess of universal remedy. We have experimentally validated nine PanA-neutralized TA pairs. While the majority of validated PanA-neutralized toxins act as translation inhibitors or membrane disruptors, a putative nucleotide cyclase toxin from a Burkholderia prophage compromises transcription and translation as well as inducing RelA-dependent accumulation of the nucleotide alarmone (p)ppGpp. We find that Panacea-containing antitoxins form a complex with their diverse cognate toxins, characteristic of the direct neutralization mechanisms employed by Type II TA systems. Finally, through directed evolution, we have selected PanA variants that can neutralize noncognate TA toxins, thus experimentally demonstrating the evolutionary plasticity of this hyperpromiscuous antitoxin domain.
Functional Interactions of metalloprotein YbeY, involved in ribosomal metabolism, with the putative metal efflux protein YbeX
(Tartu Ülikool, 2019) Sarigül, Ismail; Maiväli, Ülo; Tenson, Tanel; Tartu Ülikool. Loodus- ja täppisteaduste valdkond
YbeY is a putative ribosomal endoribonuclease which has been implicated, among other things, to be involved in quality control of 70S ribosomes, in 17S pre-rRNA maturation and in ribosomal degradation. However, controversy reigns over its mode of action, substrates, co-factors, and interaction partners. Proposed interactors of YbeY include ribosomal protein S11, Era, YbeZ, and SpoT. In many bacteria ybeY is located in the ybeZYX-Int operon, where ybeZ encodes a PhoH subfamily protein with NTP hydrolase domain and ybeX encodes a putative Cobalt/Magnesium efflux protein. Depletion of YbeY and YbeX have largely overlapping phenotypes, including accumulation of 17S pre-rRNA and an approximately 1 kb 16S rRNA cleavage product, sensitivity to heat shock, and to the protein synthesis inhibitors chloramphenicol and erythromycin. Overexpression of the YbeY partially rescues the some of the phenotypes of ΔybeX. Taken together our results indicate a functional interaction between ybeY and ybeX.
In Vitro Studies of Persister Cells
(Microbiol Mol Biol Rev, 2020-11-11) Kaldalu, N; Hauryliuk, V; Turnbull, Kathryn Jane; Putrinš, M; Tenson, Tanel
Many bacterial pathogens can permanently colonize their host and establish either chronic or recurrent infections that the immune system and antimicrobial therapies fail to eradicate. Antibiotic persisters (persister cells) are believed to be among the factors that make these infections challenging. Persisters are subpopulations of bacteria which survive treatment with bactericidal antibiotics in otherwise antibiotic-sensitive cultures and were extensively studied in a hope to discover the mechanisms that cause treatment failures in chronically infected patients; however, most of these studies were conducted in the test tube. Research into antibiotic persistence has uncovered large intrapopulation heterogeneity of bacterial growth and regrowth but has not identified essential, dedicated molecular mechanisms of antibiotic persistence. Diverse factors and stresses that inhibit bacterial growth reduce killing of the bulk population and may also increase the persister subpopulation, implying that an array of mechanisms are present. Hopefully, further studies under conditions that simulate the key aspects of persistent infections will lead to identifying target mechanisms for effective therapeutic solutions.
Making Antimicrobial Susceptibility Testing More Physiologically Relevant with Bicarbonate?
(ASM Journals, 2022-05-17) Hinnu, Mariliis; Putrinš, Marta; Bumann, Dirk; Kogermann, Karin; Tenson, Tanel
Azithromycin is a clinically important drug for treating invasive salmonellosis despite poor activity in laboratory assays for MIC. Addition of the main buffer in blood, bicarbonate, has been proposed for more physiologically relevant and more predictive testing conditions. However, we show here that bicarbonate-triggered lowering of azithromycin MIC is entirely due to alkalization of insufficiently buffered media. In addition, bicarbonate is unlikely to be altering efflux pump activity.
RelA-SpoT Homolog toxins pyrophosphorylate the CCA end of tRNA to inhibit protein synthesis
(Cell Press, 2021-08) Brodiazhenko, Tetiana; Alves Oliveira, Sofia Raquel; Roghanian, Mohammad; Sakaguchi, Yuriko; Turnbull, Kathryn Jane; Bulvas, Ondrej; Takada, Hiraku; Tamman, Hedvig; Ainelo, Andres; Pohl, Radek; Rejman, Dominik; Tenson, Tanel; Suzuki, Tsutomu; Garcia-Pino, Abel; Atkinson, Gemma C; Haurilyiuk, Vasili; Kurata, Tatsuki
RelA-SpoT Homolog (RSH) enzymes control bacterial physiology through synthesis and degradation of the nucleotide alarmone (p)ppGpp. We recently discovered multiple families of small alarmone synthetase (SAS) RSH acting as toxins of toxin-antitoxin (TA) modules, with the FaRel subfamily of toxSAS abrogating bacterial growth by producing an analog of (p)ppGpp, (pp)pApp. Here we probe the mechanism of growth arrest used by four experimentally unexplored subfamilies of toxSAS: FaRel2, PhRel, PhRel2, and CapRel. Surprisingly, all these toxins specifically inhibit protein synthesis. To do so, they transfer a pyrophosphate moiety from ATP to the tRNA 3′ CCA. The modification inhibits both tRNA aminoacylation and the sensing of cellular amino acid starvation by the ribosome-associated RSH RelA. Conversely, we show that some small alarmone hydrolase (SAH) RSH enzymes can reverse the pyrophosphorylation of tRNA to counter the growth inhibition by toxSAS. Collectively, we establish RSHs as RNA-modifying enzymes.
Ribosomes, peptides and antibiotic resistance
(Tartu : Tartu University Press, 1997) Tenson, Tanel