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Updated: Jun 13, 2026

Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43
Published on: September 11, 2020
Assembly dynamics and stability of the pneumococcal epsilon zeta antitoxin toxin (PezAT) system from Streptococcus
Hannes Mutschler1, Jochen Reinstein, Anton Meinhart
1Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany.
Abstract:
The pneumococcal epsilon zeta antitoxin toxin (PezAT) system is a chromosomally encoded, class II toxin antitoxin system from the human pathogen Streptococcus pneumnoniae. Neutralization of the bacteriotoxic protein PezT is carried out by complex formation with its cognate antitoxin PezA. Here we study the stability of the inhibitory complex in vivo and in vitro. We found that toxin release is impeded in Escherichia coli and Bacillus subtilis due to the proteolytic resistance of PezA once bound to PezT. These findings are supported by in vitro experiments demonstrating a strong thermodynamic stabilization of both proteins upon binding. A detailed kinetic analysis of PezAT assembly revealed that these particular features of PezAT are based on a strong, electrostatically guided binding mechanism leading to a stable toxin antitoxin complex with femtomolar affinity. Our data show that PezAT complex formation is distinct to all other conventional toxin antitoxin modules and a controlled mode of toxin release is required for activation.
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