Colicin
Available protein structures: | |
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Pfam | structures / ECOD |
PDB | RCSB PDB; PDBe; PDBj |
PDBsum | structure summary |
A colicin is a type of
Structure
Channel-forming colicins (colicins A, B, E1, Ia, Ib, and N) are
Translocation
Most colicins are able to translocate the outer membrane by a two-receptor system, where one receptor is used for the initial binding and the second for translocation. The initial binding is to
Resistance
Because they target specific receptors and use specific translocation machinery, cells can make themselves resistant to the colicin by repressing or deleting the genes for these proteins. Such resistant cells may suffer the lack of a key nutrient (such as
Genetic organisation
Virtually all colicins are carried on plasmids. The two general classes of colicinogenic plasmids are large, low-copy-number plasmids, and small, high-copy-number plasmids. The larger plasmids carry other genes, as well as the colicin operon. The colicin operons are generally organized with several major genes. These include a colicin structural gene, an immunity gene, and a bacteriocin release protein (BRP), or lysis, gene. The immunity gene is often produced constitutively, while the BRP is generally produced only as a read-through of the stop codon on the colicin structural gene. The colicin itself is repressed by the SOS response and may be regulated in other ways as well.[10]
Retaining the colicin plasmid is very important for cells that live with their relatives, because if a cell loses the immunity gene, it quickly becomes subject to destruction by circulating colicin. At the same time, colicin is only released from a producing cell by the use of the lysis protein, which results in that cell's death. This suicidal production mechanism would appear to be very costly, except for the fact that it is regulated by the SOS response, which responds to significant DNA damage. In short, colicin production may only occur in terminally ill cells. The Professor Kleanthous Research Group at the University of Oxford study colicins extensively as a model system for characterising and investigating protein-protein interactions and recognition.[11]
BACTIBASE[12][13] database is an open-access database for bacteriocins including colicins (view complete list).
References
- PMID 28565527.
- PMID 14731273.
- PMID 15519318.
- ^ Cascales et al. (2007). Colicin Biology. Microbio. and Mol. Bio. Rev. 71(1), 158-229. Abstract pdf
- ^ S2CID 4237547.
- PMID 12423783.
- PMID 6253914.
- PMID 6344017.
- ^ Luria, S. E. (1969) Nobel Lecture
- PMID 25751274.
- ^ "Kleanthous Research Group". Archived from the original on 6 May 2017. Retrieved 23 May 2017.
- PMID 17941971.
- PMID 20105292.
External links
- Molecular mechanisms of colicin evolution pdf
- The newly characterized colicin Y provides evidence of positive selection in pore-former colicin diversification
- Colicin OPM database
- 3D interactive pages about colicins
- Transport Classification Database listing for colicin
- Protein Data Bank colicin listing