Korean Journal of Microbiology

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Fig. 1.

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Fig. 1. Types of bacterial toxin-antitoxin systems. In the figure, red represents toxins, green represents antitoxins, blue represents enzymes, and orange represents targets of toxin or antitoxin. SD refers to Shine-Dalgarno sequence where ribosome attaches. Each figure shows 6 different types of toxin-antitoxin (TA) system. In type I TA system, antitoxin is an antisense RNA that binds to toxin mRNA, and the duplex is degraded by RNase. In the case of type II TA system, antitoxin is a protein that interacts with toxin protein and forms a non-toxic complex. The complex works as a repressor, which binds to the promoter of TA operon. TA complex formation can be controlled by proteolysis of the antitoxin. In type III TA system, antitoxin RNA binds to toxin protein and forms a non-toxic complex. In type IV TA system, antitoxin binds to the target of toxin protein instead of toxin itself, and therefore the target escapes from degradation. In type V TA system, the antitoxin acts as RNase for toxin mRNA. Lastly, in type VI TA system, toxin protein is selectively cleaved by protease only when it forms a complex with antitoxin protein.
Korean J. Microbiol. 2021;57:1-11 https://doi.org/10.7845/kjm.2021.1009
© 2021 Korean J. Microbiol.