Recombinant Escherichia coli Endoribonuclease toxin MazF (mazF)

Function

The physiological role of this TA system is debated. Programmed cell death (PCD) occurs when cells are at high density and depends on the presence of MazE-MazF and a quorum sensing pentapeptide, the extracellular death factor (EDF) with sequence Asn-Asn-Trp-Asn-Asn (NNWNN), probably produced from the zwf gene product glucose-6-phosphate 1-dehydrogenase (PubMed:17962566, PubMed:18310334). Cell death governed by the MazE-MazF and DinJ-YafQ TA systems seems to play a role in biofilm formation, while MazE-MazF is also implicated in cell death in liquid media (PubMed:19707553). Implicated in hydroxy radical-mediated cell death induced by hydroxyurea treatment (PubMed:20005847, PubMed:23416055). In conjunction with EDF prevents apoptotic-like death (ALD) in the presence of DNA damaging agents, probably by reducing recA mRNA levels in a non-endonuclease-mediated manner (PubMed:22412352). Other studies (in strains BW25113 and MC4100, the latter makes EDF) demonstrate MazF does not cause PCD but instead bacteriostasis and possibly a dormant state as well as persister cell generation (PubMed:24375411)

Subunit

Probably a dimer. Forms a heterohexamer composed of alternating toxin and antitoxin homodimers MazF(2)-MazE(2)-MazF(2). The binding site of MazE and ssRNA or ssDNA are largely overlapping; the presence of only 1 MazE molecule inhibits mRNA endoribonuclease activity. Binds to EDF but not a mutated EDF (NNGNN) (PubMed:21419338)

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