Colicine
Colicins are poisons produced by bacteria - mostly E. coli bacteria ( Escherichia coli ) - which are toxic to some strains of E. coli . They are therefore part of the bacteriocins .
Colicins are produced, among other things, by E. coli bacteria , which belong to the intestinal bacteria . Colicins consist of at least three domains , an N-terminal translocation domain, which is responsible for transport across the outer membrane, a central domain, which is responsible for recognizing the receptor, and a C-terminal toxic domain. Bacteria that are attacked by Colicins can protect themselves by producing immunity proteins.
There are different types of colicins that differ in the way their toxic domains work. There are pore-forming colicins, colicins that block translation (D), colicins that act as DNA or rRNA endonucleases (E2, E7-E9) and colicins that prevent the synthesis of murein for the cell wall (M).
Pore-shaping colcines
Some (Colicin A, B, E1, Ia, Ib, K, L, N, U, V, 5, 10) infiltrate the cell membrane (inner membrane) of the target bacteria, where they form ion channels and act as pore-forming toxins . Because of these pores, the cell membrane depolarizes, which ensures that the infected bacteria die.
One example is colicin I, which docks to an external receptor on the target cell and is directed into the periplasm there . When it reaches the cytoplasmic membrane, it forms channels through which potassium and magnesium ions as well as phosphorylated molecules flow out of the cell. This prevents the proton motor ATP synthesis . The infected cell becomes increasingly depleted in ATP and dies as a result.
The canal-forming colicins are grouped into four families:
| family | TCDB identifier | Examples | UniProt | Taxa |
|---|---|---|---|---|
| Channel-forming colicins | 1.C.1 | Colicin 1a | P06716 | E. coli |
| Colicin 1b, A, B, E, K, 10; Alveicin | Plasmids of gram-negative bacteria | |||
| Channeling Colicin V | 1.C.31 | Colicin V (Microcin) | P22522 | E. coli |
| Colicin L, microsin M. | enteral bacteria | |||
| Colicin J lysis proteins | 9.A.13 | Cjl | Q934C7 | bacteria |
| Colicin Lysis Proteins | 9.B.41 | Colicin E1 lysis protein | P05821 | enteral bacteria |
Nucleases
Other (colicin E2, colicin E7-E9) in turn destroy the DNA of the infected bacteria by an endo- DNase or rRNA of bacteria infected by a RNase.
Translocation
Most colicins are transported across the membrane with the help of two different molecules: the first is required for the first binding to the target cell, the second for the translocation. For the first binding to the target cell, the receptor recognition domain binds to a receptor in the outer membrane. These are often porins , such as OmpF, FepA, BtuB, Cir and FhuA.
Periplasmic proteins such as TolA, TolB, TolC or TonB are required for transport through the outer membrane. Based on these periplasmic proteins, colicins can be classified as group A or group B colicins. Group A uses the Tol system, which consists of TolA, TolQ and TolR. These include the Colicins A, E1, E2-4, E6-9, N and U. Group B uses the tone system, which consists of TonB, ExbB and ExbD. These include the colicins B, D, G, H, Ia, Ib, M, 5 and 10. Table 2 lists the colicins of groups A and B with their receptors which they use for the first binding.
| Colicin | receptor | Periplasmic system | group | toxic domain | Immunity protein group
(only for pores) |
|---|---|---|---|---|---|
| A. | BtuB / OmpF | Tol | A. | pore | A. |
| B. | FepA | volume | B. | pore | A. |
| D. | FepA | volume | B. | Translation inhibitor | |
| E1 | BtuB / TolC | Tol | A. | pore | E1 |
| E2, E7-9 | BtuB / OmpF | Tol | A. | Nuclease | |
| E3, E4, E6 | BtuB / OmpF | Tol | A. | Nuclease, | |
| E5 | |||||
| FY | Yiu | volume | B. | pore | |
| G *, H * | Fiu | volume | B. | - | |
| Ia, Ib | Cir | volume | B. | pore | E1 |
| K | pore | E1 | |||
| N | OmpF / OmpC / Phoe | Tol | A. | pore | A. |
| M. | FhuA | volume | B. | Murein synthesis inhibitor | |
| U | OmpA / OmpF / LPS | Tol | A. | pore | A. |
| 5, 10 | Tsx | volume | B. | pore | E1 |
| 28B (previously Colicin L) | pore |
* Colicin G and H are now classified as microsines and are therefore not colicins.
How the colicins are transported through the outer membrane is not yet known for most colicins. However, it has been shown that Colicin M is unfolded for import into the periplasm, i.e. for transport through the outer membrane. In the periplasm, it is folded again with the help of the chaperone FkpA.
immunity
The immunity proteins protect against the toxic effects of the colicins by binding to them. Each colicin requires its own specific immunity protein. The immunity proteins of pore-forming bacteriocins are classified into either the group of E1-like or A-like immunity proteins based on DNA sequence comparisons. The immunity proteins of the E1 group are similar to the immunity protein of colicin E1 and have 3 transmembrane helixes. The immunity proteins of the A group are similar to the immunity protein of colicin A and have 4 transmembrane helixes.
literature
- A. Gratia: Sur un remarquable exemple d'antagonisme entre deux souches de colibacille. In: Compt. Rend. Soc. Biol. Volume 93, 1925, pp. 1040-1042.
- JP Gratia: Andre Gratia: a forerunner in microbial and viral genetics. In: Genetics. Volume 156, No. 2, 2000, pp. 471-476. PMID 11014798 ; PMC 1461273 (free full text, PDF).
- K. Schaller, M. Nomura: Colicin E2 is DNA endonuclease . In: Proc Natl Acad Sci US A. 1976. PMID 1069283
Individual evidence
- ↑ Stanislav D. Zakharov, Elena A. Kotova, Yuri N. Antonenko, William A. Cramer: On the role of lipid in colicin pore formation . In: Biochimica Et Biophysica Acta . tape 1666 , no. 1-2 , November 3, 2004, pp. 239-249 , doi : 10.1016 / j.bbamem.2004.07.001 , PMID 15519318 .
- ↑ a b Grigorios Papadakos, Justyna A. Wojdyla, Colin Kleanthous: Nuclease colicins and their immunity proteins . In: Quarterly Reviews of Biophysics . tape 45 , no. 1 , February 1, 2012, p. 57-103 , doi : 10.1017 / S0033583511000114 , PMID 22085441 .
- ↑ Jacqueline L. Hilsenbeck, HaJeung Park, Gregory Chen, Buhyun Youn, Kathleen Postle: Crystal structure of the cytotoxic bacterial protein colicin B at 2.5 A resolution . In: Molecular Microbiology . tape 51 , no. 3 , February 1, 2004, p. 711-720 , PMID 14731273 .
- ↑ a b Zhenghua Cao, Phillip E. Klebba: Mechanisms of colicin binding and transport through outer membrane porins . In: Biochemistry . tape 84 , no. 5-6 , June 1, 2002, pp. 399-412 , PMID 12423783 .
- ↑ a b Karla D. Krewulak, Hans J. Vogel: TonB or not TonB: is that the question? In: Biochemistry and Cell Biology = Biochimie Et Biologie Cellulaire . tape 89 , no. 2 , April 1, 2011, p. 87-97 , doi : 10.1139 / o10-141 , PMID 21455261 .
- ↑ D. Smajs, H. Pilsl, V. Braun: Colicin U, a novel colicin produced by Shigella boydii. In: Journal of bacteriology. Volume 179, Number 15, August 1997, pp. 4919-4928, PMID 9244283 , PMC 179342 (free full text).
- ↑ Julia Hullmann, Silke I. Patzer, Christin Römer, Klaus Hantke, Volkmar Braun: Periplasmic chaperone FkpA is essential for imported colicin M toxicity . In: Molecular Microbiology . tape 69 , no. 4 , August 1, 2008, p. 926-937 , doi : 10.1111 / j.1365-2958.2008.06327.x , PMID 18554332 .
- ↑ Eric Cascales et al .: Colicin Biology . In: MICROBIOLOGY AND MOLECULAR BIOLOGY REVIEWS , 71.1 (2007), 158-229. doi : 10.1128 / MMBR.00036-06 .