Toxin-Antitoxin Systems

Toxin-antitoxin or TA systems are operons encoding a stable toxin and a labile antidote. They play a major role in bacterial stress physiology by temporarily halting cell division when nutrients are scarce. They are proposed to be involved in multidrug resistance. Many different families of TA modules exist, differing in the cellular target of the toxin and the nature of the DNA binding domain employed by the antitoxin.
One family, ccdAB, interferes with replication and transcription via interactions with gyrase. This family has been extensively studied in the last five years, leading to a detailed understanding on how the toxin CcdB poisons DNA-bound-gyrase and how the intrinsically disordered domain of the antitoxin CcdA is able to rejuvenated CcdB-poisoned gyrase. The latter proves to be an example on how intrinsically disordered proteins act in mechanistic terms and why intrinsic disorder is required in certain biochemical contexts.
Another family of TA modules, phd/doc, inhibit translation by interfering with the action of the ribosome. The phd/doc module of bacteriophage P1 is being used to study transcription regulation by conditional co-operativity. This is a novel regulatory mechanism used by bacteria that involves allosteric communication between two (partly) disordered protein domains. While such a form of allostery has been predicted based on theoretical arguments, our work provided the first experimental evidence of that such a mechanisms is effectively used by certain organisms.
 
Contact: Prof. dr. Remy Loris

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