Regulation of toxin-antitoxin systems by proteolysis.

Toxin-antitoxin systems are widely distributed among many bacterial species, including human pathogens. Typically, these systems consist of two genes in an operon which encodes a stable toxin disrupting essential cellular processes and a labile antitoxin preventing toxicity. Regulation of type II TA system in which both components are proteins, relies on proteolysis. In this paper, we outline the significant features of antitoxin proteins important for proteolysis. We present examples of best known processes of antitoxin degradation by specific proteases mainly in Escherichia coli, but are also included intensively studied systems from other bacteria. The effect of environmental conditions on regulation and activity of TA systems and on consequences of proteolytic activity are discussed.