Part:BBa_K4782007

lldR + ColE1 immunity protein

Name: P9 + lldR + RBS + ColE1 immunity protein
length: 1209 bp
Origin: Escherichia coli, synthetic
Function: Expression of regulatory LldR and ColE1 immunity protein
Properties: regulatory biobrick for BBa_K3606018, BBa_K1847001, BBa_BBa_K2922025

Sequence and Features

Assembly Compatibility:

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

  Illegal BglII site found at 36
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal AgeI site found at 630
  
• 1000
  COMPATIBLE WITH RFC[1000]

Colicin E1 immunity protein

The bacteria are protected from colicin's effects by immunity proteins. With the N terminus in the cytoplasm and the C terminus in the periplasm, the colicin E1 immunity protein (Cei) crosses the cytoplasmic membrane three times, having approximately 170 residues. ^[1]
The immunity protein produced by the same colicinogenic plasmid effectively counteracts the deadly effects of a colicin that forms channels. Membrane proteins with three or four transmembrane domains make up the immune proteins that natural colicinogenic plasmids constitutively express. They provide defense against the colicin molecules ingested by colicinogenic bacteria by attaching to and deactivating cytotoxic domains. The cell that makes intracellular colicin is not impacted by it in any way ^[2]
According to reports, the C-terminus of the colicin interacts very specifically with the immunity protein to cause neutralization. In order to stop the domain from attacking the cell's own mechanisms, this usually entails attaching to and inhibiting the domain's active site ^[2] The immunity proteins are no longer required once they are released from the generating cell because the cytotoxic domain must become active once a target cell has been penetrated. When it binds to an outer membrane receptor on the target cell, it often gets disassociated from the colicin.

LldR Regulatory Protein

LlDR is a protein that blocks O1 and O2 regions of ALPaGA promoter by binding to them and inhibiting RNA polymerase from starting the transcription. When the L-lactate is present, it is transported to the cell, binding to the LldR and changing the conformation of the loop. In this plasmid, it is present as a different gene under the P9 promoter.

References

[1] Song, H. Y., & Cramer, W. A. (1991). Membrane topography of ColE1 gene products: the immunity protein. Journal of bacteriology, 173(9), 2935-2943.
[2] Alonso, G., Vílchez, G., & Lemoine, V. R. (2000). How bacteria protect themselves against channel-forming colicins. International Microbiology, 3(2), 81-88.
[3] Espesset, D., Piet, P., Lazdunski, C., & Géli, V. (1994). Immunity proteins to pore‐forming colicins: structure‐function relationships. Molecular microbiology, 13(6), 1111-1120.