3nfc | pdb_00003nfc

Crystal structure of E.coli MazF Toxin

spinqualitylabelsall models 3nfc, resolution 2.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3nfc is a 6 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Related: 1ub4 Resources: FirstGlance, OCA, RCSB, PDBsum Function [CHPA_ECOLI] Toxic component of a toxin-antitoxin (TA) module. MazF is a sequence-specific mRNA endoribonuclease that inhibits protein synthesis and induces bacterial stasis. It is very stable, single-strand specific and cleavage is independent of the ribosome, although translation enhances cleavage for some mRNAs. Cleavage usually occurs between the first A and C of ACA sequences, yielding a 2',3'-cyclic phosphate and a free 5'-OH. 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. This effect can be rescued by expression of MazE, but after 6 hours in rich medium overexpression of MazF leads to programmed cell death. MazF-mediated cell death occurs following a number of stress conditions in a relA-dependent fashion and only when cells are in log phase. Cell growth and viability are not affected when MazF and MazE are coexpressed. Programmed cell death occurs when cells are at high density and depends on the presence of MazEF and a quorum sensing pentapeptide, the extracellular death factor (EDF) with sequence NNWNN, probably produced from the zwg gene product glucose-6-phosphate 1-dehydrogenase. Both MazE and MazEF bind to the promoter region of the mazEF operon to inhibit their transcription. Might also serve to protect cells against bacteriophage; in the presence of MazEF fewer P1 phage are produced than in a disruption strain. For strain K38 most wild-type cells are killed by not by phage lysis; it was suggested that MazEF causes P1 phage exclusion from the bacterial population. This phenomenon is strain dependent. Cell death governed by the mazEF and dinJ-yafQ TA modules seems to play a role in biofilm formation, while mazEF is also implicated in cell death in liquid media.

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