Originally thought to regulate post-segregational killing, bacterial toxin-antitoxin systems have since been implicated in several different cellular stress responses. Type II systems, those with protein-protein toxin-antitoxin interactions, have toxins with wide-ranging functions, serving as ribonucleases, kinases, and DNA gyrase inhibitors, among others. Previous bioinformatics studies have putatively identified a number of new toxin-antitoxin families, including a pair marked only by a conserved Arg-Glu-Ser (RES) domain in the toxin. Subsequently confirmed to function as a toxin-antitoxin pair, this system remains totally uncharacterized despite being widely distributed throughout proteobacteria. Here we report the 1.5 Å resolution crystal structure of an RES domain-bearing toxin found within a lasso peptide gene cluster in complex with the C-terminal portion of its antitoxin, the first structure of its kind. We also provide initial biochemical characterization of the system, giving insight into a new toxin-antitoxin family dissimilar to any that have been characterized to date.

Biochemical and structural analysis of a novel toxin-antitoxin module

254th National Meeting (2017)

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