AbrB-like is a family of small proteins that operate in conjunction with a cognate toxin molecule. The commonly attributed role of toxin-antitoxin systems is to maintain low-copy number plasmids from one generation to the next. Such gene-pairs are also found on chromosomes and to be associated with a number of biological functions such as: reduction of protein synthesis, gene regulation and retardation of cell growth under nutritional stress [1]. This family includes proteins from a number of different pairings, eg MazE, AbrB, VapB [2], PhoU, PemI-like and SpoVT. MazE is the antidote to the toxin MazF of E. coli. MazE-MazF in E. coli is a regulated prokaryotic chromosomal addiction module. MazE antidote is degraded by the ClpPA protease of the bacterial proteasome. MazE-MazF is thought to play a role in programmed cell death when cells suffer nutrient deprivation [3], and MazE-MazF modules have also been implicated in the bacteriostatic effects of other addiction modules [3].

1: Identification of AbrB-regulated genes involved in biofilm formation by Bacillus subtilis. Hamon MA, Stanley NR, Britton RA, Grossman AD, Lazazzera BA; Mol Microbiol. 2004;52:847-860. PMID:15101989

2: Crystal structure of the DNA-bound VapBC2 antitoxin/toxin pair from Rickettsia felis. Mate MJ, Vincentelli R, Foos N, Raoult D, Cambillau C, Ortiz-Lombardia M; Nucleic Acids Res. 2012;40:3245-3258. PMID:22140099

3: Crystal structure of the MazE/MazF complex: molecular bases of antidote-toxin recognition. Kamada K, Hanaoka F, Burley SK; Mol Cell. 2003;11:875-884. PMID:12718874