Endoribonuclease ToxN - B8X8Z0 (TOXN_PECAT)

 

Protein Feature View of PDB entries mapped to a UniProtKB sequence  

  • Number of PDB entries for B8X8Z0: 3
 
Function
Toxic component of a type III toxin-antitoxin (TA) module. An endoribonuclease which is active independently of the ribosome, cleaving between the second and third A of AAA(U/G) sequences, although not all occurrences of this tetranucleotide are cleaved (PubMed:23267117). Digests many mRNA species, including its own transcript and its cognate antitoxin RNA ToxI. ToxI has 5.5 nearly identical 36 nucleotide-long repeats (a single repeat neutralizes the toxin in vivo); a single repeat folds into a pseudoknot which binds the toxin (PubMed:21240270). The ToxI precursor RNA is a preferential target in vivo and is progressively degraded to single repeat lengths as ToxN-ToxI complex self-assembly occurs (PubMed:23267117). In vivo expression of ToxI antitoxin inhibits endonuclease activity of ToxN (PubMed:23267117). The toxin alone inhibits growth when expressed in E.coli without causing cell lysis; this bacteriostatic effect is neutralized by cognate RNA antitoxin ToxI (PubMed:19124776, PubMed:23267117). Non-cognate antitoxin RNA from B.thuringiensis does not inhibit this toxin (PubMed:23267117). The RNA antitoxin is less stable than the proteinaceous toxin; synthesis of ToxI in the absence of new ToxN synthesis restores growth and also detectable accumulation of the ToxN protein (PubMed:19124776). Negatively regulates its own operon in complex with ToxI (PubMed:19633081). The toxin-antitoxin pair function in plasmid maintenance (a plasmid addiction system) (PubMed:23267117). UniProt
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Subunit Structure
One ToxN monomer binds to a 36-nt-long single repeat of the ToxI RNA; this complex forms a triangular heterohexameric complex with ToxN connected by the ToxI RNA to another toxin molecule. The ToxI repeat forms a pseudoknot which occludes the toxin active site. Interaction of ToxI with ToxN partially inhibits the latter's endoribonuclease activity in vitro (PubMed:21240270). The complex self-assembles in vitro with either full-length or processed single repeats; during the process the precursor is processed (PubMed:23267117). UniProt
  • Organism: Erwinia carotovora subsp. atroseptica
  • Length:
  • UniProt
  • Other Gene names: toxN
This protein in other organisms (by gene name):
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Data in green originates from UniProtKB  
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Data in orange originates from the SCOP   (version 1.75) and SCOPe   (version 2.04) classifications.
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The PDB to UniProt mapping is based on the data provided by the EBI SIFTS project. See also Velankar et al., Nucleic Acids Research 33, D262-265 (2005).
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