Part:BBa_K2433001

ietS

ietS is the gene encoding the toxin in the toxin antitoxin system ietAS native to tumor-inducing (Ti) plasmids of Agrobacterium tumefaciens. This part comes from the nopaline type Ti plasmid pTiC58. The ietAS operon was given its name after the incompatibility enhancer of the Ti plasmid. In combination with the antitoxin gene, this part has been shown in literature to be important in reducing the transconjugant efficiency for different incoming Ti plasmids as well as contributing to the stability of plasmids harboring this construct.

In toxin/antitoxin systems, the toxin is always a protein. Data base searches have shown that IetS is similar in structure to serine proteases. Toxins are more stable than their cognate antitoxins, but they are expressed at lower levels. In functioning toxin/antitoxin systems, the antitoxin forms a protein complex with the toxin, neutralizing it and preventing cell termination.

When a plasmid loses its toxin/antitoxin construct, antitoxin levels become depleted due to rapid degradation by proteases. This enables the toxin, in this case ietS, to exert its toxicity on the host cell, inhibiting growth.

ietAS was shown to enhance the incompatibility and stability of the Ti plasmid in Agrobacterium tumefaciens, however, the presence of ietAS showed no effect when tested in E. coli. (Yamamoto et al., 2009)

When tested on its own under a constitutive promoter, ietS was shown to be toxic to Agrobacterium tumefaciens, however, it as no effect in E. coli. (Yamamoto et al., 2009)

References
Melderen, L. V., & Bast, M. S. (2009). Bacterial Toxin–Antitoxin Systems: More Than Selfish Entities? PLoS Genetics, 5(3). doi:10.1371/journal.pgen.1000437
Unterholzner, S. J., Poppenberger, B., & Rozhon, W. (2013). Toxin–antitoxin systems: Biology, identification, and application. Mobile Genetic Elements, 3(5), e26219. http://doi.org/10.4161/mge.26219
Yamamoto, S., Kiyokawa, K., Tanaka, K., Moriguchi, K., & Suzuki, K. (2009). Novel Toxin-Antitoxin System Composed of Serine Protease and AAA-ATPase Homologues Determines the High Level of Stability and Incompatibility of the Tumor-Inducing Plasmid pTiC58. Journal of Bacteriology, 191(14), 4656-4666. doi:10.1128/jb.00124-09

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal BamHI site found at 425
  Illegal XhoI site found at 2020
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal NgoMIV site found at 1330
  Illegal NgoMIV site found at 2214
  Illegal AgeI site found at 2371
  
• 1000
  INCOMPATIBLE WITH RFC[1000]

  Illegal BsaI.rc site found at 505
  Illegal BsaI.rc site found at 1690
  Illegal BsaI.rc site found at 1972