A novel gyrase inhibitor from toxin–antitoxin system expressed by Staphylococcus aureus

• Published in: The FEBS journal Vol. 290; no. 6; pp. 1502 - 1518
• Main Authors: Kato, Fuminori, Yamaguchi, Yoshihiro, Inouye, Keiko, Matsuo, Koichi, Ishida, Yojiro, Inouye, Masayori
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.03.2023
• Subjects: Antitoxins; Antitoxins - genetics; Bacterial Proteins - metabolism; Biocompatibility; Deoxyribonucleic acid; Dichroism; DNA; DNA biosynthesis; DNA Gyrase - genetics; DNA gyrase inhibitor; DNA topoisomerase; E coli; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Genomes; Neural networks; Plasmids; Protein biosynthesis; Protein structure; Protein synthesis; Residues; Ribonucleic acid; RNA; Secondary structure; Site-directed mutagenesis; Spectroscopy; Staphylococcus aureus; Staphylococcus aureus - genetics; Staphylococcus aureus - metabolism; Toxicity; Toxin-Antitoxin Systems - genetics; Toxins; Toxins and antitoxins; toxin–antitoxin system; Transcription; secondary structure; site-directed mutagenesis; toxin-antitoxin system; DNA gyrase inhibitor; Staphylococcus aureus
• ISSN: 1742-464X; 1742-4658
• DOI: 10.1111/febs.16634

Toxin–antitoxin (TA) systems consist of a toxin inhibiting essential cellular functions (such as DNA, RNA and protein synthesis), and its cognate antitoxin neutralizing the toxicity. Recently, we identified a TA system termed TsbA/TsbT in the Staphylococcus aureus genome. The induction of the tsbT gene in Escherichia coli halted both DNA and RNA synthesis, reduced supercoiled plasmid and resulted in increasingly relaxed DNA. These results suggested that DNA gyrase was the target of TsbT. In addition, TsbT inhibited both E. coli and S. aureus DNA gyrase activity and induced linearization of plasmid DNA in vitro. Taken together, these results demonstrate that the TsbT toxin targets DNA gyrase in vivo. Site‐directed mutagenesis experiments showed that the E27 and D37 residues in TsbT are critical for toxicity. Secondary structure prediction combining the analysis of vacuum‐ultraviolet circular‐dichroism spectroscopy and neural network method demonstrated that the 22nd–32nd residues of TsbT form an α‐helix structure, and that the E27 residue is located around the centre of the α‐helix segment. These findings give new insights not only into S. aureus TA systems, but also into bacterial toxins targeting DNA topoisomerases. Bacterial toxin–antitoxin (TA) systems consist of a toxin inhibiting essential cellular functions. Here, we demonstrated that a novel TsbT toxin expressed by Staphylococcus aureus targets DNA gyrase, a bacterial topoisomerase. Moreover, we showed that the E27 and D37 residues in TsbT are critical for its toxicity, and the 22nd–32nd residues of TsbT form an α‐helix structure.