Colicin N

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Colicin N is a type of Colicin, a bacteriocin made by E. coli which acts against other nearby E. coli to kill them by forming a pore in the membrane, leading to depolarisation of the membrane which kills the cell.

Contents

Synthesis and release

The plasmid encoding the c. 42kDa[1] ColN also encodes its corresponding Colicin Immunity Protein, Cni, in order to protect the colicinergic cell from the cytotoxic activity of the colicin.

Mechanism of uptake

Colicin N parasitizes the outer membrane protein F (OmpF) as both its receptor and its translocator, alongside the Tol proteins TolQRA. There is evidence to show that the translocation may occur at the protein-lipid interface. ColN binding displaces OmpF-bound lipopolysaccharide, the major lipid in the outer leaflet of the outer membrane. The N terminal region of ColN then rearranges and binds to OmpF[2]. As only OmpF is required, this may reveal how a general translocation route for a number of colicins may function[3]. However there is no evidence that this simply forms a pore for translocation, more work is needed to establish the translocation mechanism[4].

Killing Activities

Colicin N depolarises the E. coli membrane, leading to lysis of the cell, and the cytotoxic domain that initiates this reaction is highly homologous to the C-terminal domain of ColA[5].

References

  1. ↑ Pugsley AP. Genetic analysis of ColN plasmid determinants for colicin production, release, and immunity. J Bacteriol. 1984 May;158(2):523-9. PMID:6327609
  2. ↑ Baboolal TG, Conroy MJ, Gill K, Ridley H, Visudtiphole V, Bullough PA, Lakey JH. Colicin N binds to the periphery of its receptor and translocator, outer membrane protein F. Structure. 2008 Mar;16(3):371-9. PMID:18334212 doi:10.1016/j.str.2007.12.023
  3. ↑ Vetter IR, Parker MW, Tucker AD, Lakey JH, Pattus F, Tsernoglou D. Crystal structure of a colicin N fragment suggests a model for toxicity. Structure. 1998 Jul 15;6(7):863-74. PMID:9687368
  4. ↑ Sharma O, Yamashita E, Zhalnina MV, Zakharov SD, Datsenko KA, Wanner BL, Cramer WA. Structure of the complex of the colicin E2 R-domain and its BtuB receptor. The outer membrane colicin translocon. J Biol Chem. 2007 Aug 10;282(32):23163-70. Epub 2007 Jun 4. PMID:17548346 doi:10.1074/jbc.M703004200
  5. ↑ Pugsley AP. Nucleotide sequencing of the structural gene for colicin N reveals homology between the catalytic, C-terminal domains of colicins A and N. Mol Microbiol. 1987 Nov;1(3):317-25. PMID:2834623

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