Toxic component of a type II toxin-antitoxin (TA) system. MazF is a sequence-specific endoribonuclease that inhibits protein synthesis and induces bacterial stasis. It is very stable, single-strand specific and cleavage is independent of the ribosome. The endoribonuclease activity (a toxin) is inhibited by the labile cognate antitoxin MazE. Toxicity results when the levels of MazE decrease in the cell, leading to mRNA degradation. Both MazE and MazE-MazF bind to the promoter region of the mazE-mazF operon to inhibit their transcription. Probably a dimer. Forms a heterohexamer composed of alternating toxin and antitoxin homodimers MazF(2)-MazE(2)-MazF(2). Belongs to the PemK/MazF family.