Crystal structure of the MazE/MazF complex: Molecular bases of antidote-toxin recognition

Abstract

A structure of the Escherichia coli chromosomal MazE/MazF addiction module has been determined at 1.7 Å resolution. Addiction modules consist of stable toxin and unstable antidote proteins that govern bacterial cell death. MazE (antidote) and MazF (toxin) form a linear heterohexamer composed of alternating toxin and antidote homodimers (MazF2-MazE2-MazF2). The MazE homodimer contains a β barrel from which two extended C termini project, making interactions with flanking MazF homodimers that resemble the plasmid-encoded toxins CcdB and Kid. The MazE/MazF heterohexamer structure documents that the mechanism of antidote-toxin recognition is common to both chromosomal and plasmid-borne addiction modules, and provides general molecular insights into toxin function, antidote degradation in the absence of toxin, and promoter DNA binding by antidote/toxin complexes.