Antitoxin component of a type II toxin-antitoxin (TA) system. Neutralizes the effect of cognate toxin MazF. In M.smegmatis 3 TA systems (VapB-VapC, MazE-MazF and Phd-Doc) may be involved in monitoring the nutritional supply and physiological state of the cell, linking catabolic with anabolic reactions. Forms a complex with cognate toxin MazF. Constitutively expressed during exponential growth and early stationary phase, it decreases in late stationary phase; part of the mazE-mazF operon. Negatively autoregulated by one or both of MazE-MazF. The mazE-mazF operon is not essential. A triple TA mutant (missing vapB-vapC, mazE-mazF and phd-doc TA systems) survives antibiotic challenge, suggesting the TA systems are not required to generate drug-resistant cells. However the mutant is more sensitive to oxidative and heat stress, and does not survive long term starvation during aerobic growth on complex medium. There is a difference in the level of branched-chain amino acids, which may play a role in monitoring the nutritional supply and physiological state of the cell.