Background: Xenorhabdus nematophila maintains species-specific mutual interaction
with nematodes of Steinernema genus. Type II Toxin Antitoxin (TA) systems, the mazEF TA system
controls stress and programmed cell death in bacteria.
Objective: This study elucidates the functional characterization of Xn-mazEF, a mazEF homolog in
X. nematophila by computational and in vitro approaches.
Methods: 3D- structural models for Xn-MazE toxin and Xn-MazF antitoxin were generated, validated
and characterized for protein - RNA interaction analysis. Further biological and cellular functions
of Xn-MazF toxin were also predicted. Molecular dynamics simulations of 50ns for Xn-
MazF toxin complexed with nucleic acid units (DU, RU, RC, and RU) were performed. The MazF
toxin and complete MazEF operon were endogenously expressed and monitored for the killing of
Escherichia coli host cells under arabinose induced tightly regulated system.
Results: Upon induction, E. coli expressing toxin showed rapid killing within four hours and attained
up to 65% growth inhibition, while the expression of the entire operon did not show significant
killing. The observation suggests that the Xn-mazEF TA system control transcriptional regulation
in X. nematophila and helps to manage stress or cause toxicity leading to programmed death of
Conclusion: The study provides insights into structural and functional features of novel toxin, Xn-
MazF and provides an initial inference on control of X. nematophila growth regulated by TA systems.