title: Assembly dynamics and stability of the pneumococcal epsilon zeta antitoxin toxin (PezAT) system from Streptococcus pneumoniae.
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.
authors.affiliation: Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany.
authors.forename: Hannes
authors.initials: H
authors.lastname: Mutschler
authors.forename: Jochen
authors.initials: J
authors.lastname: Reinstein
authors.forename: Anton
authors.initials: A
authors.lastname: Meinhart
mesh_terms: D000992:Antitoxins / Q000737:chemistry*; D001412:Bacillus subtilis / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D005456:Fluorescent Dyes / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D007700:Kinetics; D008954:Models, Biological; D015233:Models, Statistical; D008968:Molecular Conformation; D025941:Protein Interaction Mapping; D055672:Static Electricity; D013296:Streptococcus pneumoniae / Q000378:metabolism*; D013816:Thermodynamics; D013997:Time Factors; D014118:Toxins, Biological / Q000737:chemistry
chemical_list: D000992:Antitoxins; D005456:Fluorescent Dyes; D014118:Toxins, Biological