Colicin

Last updated
Colicin
PDB 2ivz EBI.jpg
Structure of TolB in complex with a peptide of the colicin e9 t-domain
Identifiers
SymbolColicin
Pfam PF03515
Pfam clan CL0446
InterPro IPR003058
SCOP2 1jch / SCOPe / SUPFAM
Available protein structures:
Pfam   structures / ECOD  
PDB RCSB PDB; PDBe; PDBj
PDBsum structure summary

A colicin is a type of bacteriocin produced by and toxic to some strains of Escherichia coli . [1] Colicins are released into the environment to reduce competition from other bacterial strains. Colicins bind to outer membrane receptors, using them to translocate to the cytoplasm or cytoplasmic membrane, where they exert their cytotoxic effect, including depolarisation of the cytoplasmic membrane, DNase activity, RNase activity, or inhibition of murein synthesis.

Contents

Structure

Channel-forming colicins (colicins A, B, E1, Ia, Ib, and N) are transmembrane proteins that depolarize the cytoplasmic membrane, leading to dissipation of cellular energy. [2] These colicins contain at least three domains: an N-terminal translocation domain responsible for movement across the outer membrane and periplasmic space (T domain); a central domain responsible for receptor recognition (R domain); and a C-terminal cytotoxic domain responsible for channel formation in the cytoplasmic membrane (C domain). [3] [4] [5] R domain regulates the target and binds to the receptor on the sensitive cell. T domain is involved in translocation, co-opting the machinery of the target cell. The C domain is the 'killing' domain and may produce a pore in the target cell membrane, or act as a nuclease to chop up the DNA or RNA of the target cell. [5]

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 cell surface receptors such as the outer membrane proteins OmpF, FepA, BtuB, Cir and FhuA; colicins have been classified according to which receptors they bind to. The presence of specific periplasmic proteins, such as TolA, TolB, TolC, or TonB, are required for translocation across the membrane. [6] Cloacin [7] DF13 is a bacteriocin that inactivates ribosomes by hydrolysing 16S RNA in 30S ribosomes at a specific site. [8]

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 iron or a B vitamin), but benefit by not being killed. Colicins exhibit a '1-hit killing kinetic' [ citation needed ] which does not necessarily mean a single molecule is sufficient to kill, but certainly that it only takes a small number. In his 1969 Nobel Laureate speech, Salvador E. Luria speculated that colicins could only be this toxic by causing a domino effect that destabilized the cell membrane. [9] He was not entirely correct, but pore-forming colicins do depolarize the membrane and thus eliminate the energy source for the cell. The colicins are highly effective toxins.[ citation needed ]

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).

Related Research Articles

<span class="mw-page-title-main">Bacteriocin</span> Class of bacterially produced peptide antibiotics

Bacteriocins are proteinaceous or peptidic toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s). They are similar to yeast and paramecium killing factors, and are structurally, functionally, and ecologically diverse. Applications of bacteriocins are being tested to assess their application as narrow-spectrum antibiotics.

<span class="mw-page-title-main">Secretion</span> Controlled release of substances by cells or tissues

Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical mechanism of cell secretion is via secretory portals at the plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structures embedded in the cell membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell.

<span class="mw-page-title-main">Bacterial outer membrane</span>

The bacterial outer membrane is found in gram-negative bacteria. Its composition is distinct from that of the inner cytoplasmic cell membrane - among other things, the outer leaflet of the outer membrane of many gram-negative bacteria includes a complex lipopolysaccharide whose lipid portion acts as an endotoxin - and in some bacteria such as E. coli it is linked to the cell's peptidoglycan by Braun's lipoprotein.

Adenylate cyclase toxin is a virulence factor produced by some members of the genus Bordetella. Together with the pertussis toxin it is the most important virulence factor of the causative agent of whooping cough, Bordetella pertussis. Bordetella bronchiseptica and Bordetella parapertussis, also able to cause pertussis-like symptoms, also produce adenylate cyclase toxin. It is a toxin secreted by the bacteria to influence the host immune system.

<span class="mw-page-title-main">Anthrax toxin</span> Tripartite protein complex secreted by virulent strains of Bacillus anthracis

Anthrax toxin is a three-protein exotoxin secreted by virulent strains of the bacterium, Bacillus anthracis—the causative agent of anthrax. The toxin was first discovered by Harry Smith in 1954. Anthrax toxin is composed of a cell-binding protein, known as protective antigen (PA), and two enzyme components, called edema factor (EF) and lethal factor (LF). These three protein components act together to impart their physiological effects. Assembled complexes containing the toxin components are endocytosed. In the endosome, the enzymatic components of the toxin translocate into the cytoplasm of a target cell. Once in the cytosol, the enzymatic components of the toxin disrupts various immune cell functions, namely cellular signaling and cell migration. The toxin may even induce cell lysis, as is observed for macrophage cells. Anthrax toxin allows the bacteria to evade the immune system, proliferate, and ultimately kill the host animal. Research on anthrax toxin also provides insight into the generation of macromolecular assemblies, and on protein translocation, pore formation, endocytosis, and other biochemical processes.

Cytolysin refers to the substance secreted by microorganisms, plants or animals that is specifically toxic to individual cells, in many cases causing their dissolution through lysis. Cytolysins that have a specific action for certain cells are named accordingly. For instance, the cytolysins responsible for the destruction of red blood cells, thereby liberating hemoglobins, are named hemolysins, and so on. Cytolysins may be involved in immunity as well as in venoms.

<span class="mw-page-title-main">Fas receptor</span> Mammalian protein found in Homo sapiens

The Fas receptor, also known as Fas, FasR, apoptosis antigen 1, cluster of differentiation 95 (CD95) or tumor necrosis factor receptor superfamily member 6 (TNFRSF6), is a protein that in humans is encoded by the FAS gene. Fas was first identified using a monoclonal antibody generated by immunizing mice with the FS-7 cell line. Thus, the name Fas is derived from FS-7-associated surface antigen.

<span class="mw-page-title-main">Maltose-binding protein</span>

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<span class="mw-page-title-main">Hemolysin</span> Molecule destroying the membrane of red blood cells

Hemolysins or haemolysins are lipids and proteins that cause lysis of red blood cells by disrupting the cell membrane. Although the lytic activity of some microbe-derived hemolysins on red blood cells may be of great importance for nutrient acquisition, many hemolysins produced by pathogens do not cause significant destruction of red blood cells during infection. However, hemolysins are often capable of lysing red blood cells in vitro.

<span class="mw-page-title-main">Outer membrane receptor</span>

Outer membrane receptors, also known as TonB-dependent receptors, are a family of beta barrel proteins named for their localization in the outer membrane of gram-negative bacteria. TonB complexes sense signals from the outside of bacterial cells and transmit them into the cytoplasm, leading to transcriptional activation of target genes. TonB-dependent receptors in gram-negative bacteria are associated with the uptake and transport of large substrates such as iron siderophore complexes and vitamin B12.

<span class="mw-page-title-main">Class II bacteriocin</span>

Class II bacteriocins are a class of small peptides that inhibit the growth of various bacteria.

Streptolysins are two hemolytic exotoxins from Streptococcus. Types include streptolysin O, which is oxygen-labile, and streptolysin S, which is oxygen-stable.

'Staphylococcus aureus delta toxin is a toxin produced by Staphylococcus aureus. It has a wide spectrum of cytolytic activity.

<span class="mw-page-title-main">Clostridium difficile toxin B</span>

Clostridium difficile toxin B is a cytotoxin produced by the bacteria Clostridioides difficile, formerly known as Clostridium difficile. It is one of two major kinds of toxins produced by C. difficile, the other being an related enterotoxin. Both are very potent and lethal.

The RTX toxin superfamily is a group of cytolysins and cytotoxins produced by bacteria. There are over 1000 known members with a variety of functions. The RTX family is defined by two common features: characteristic repeats in the toxin protein sequences, and extracellular secretion by the type I secretion systems (T1SS). The name RTX refers to the glycine and aspartate-rich repeats located at the C-terminus of the toxin proteins, which facilitate export by a dedicated T1SS encoded within the rtx operon.

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<span class="mw-page-title-main">Bacteriocin IId</span>

Bacteriocin AS-48 is a cyclic peptide antibiotic produced by the eubacteria Enterococcus faecalis that shows a broad antimicrobial spectrum against both Gram-positive and Gram-negative bacteria. Bacteriocin AS-48 is encoded by the pheromone-responsive plasmid pMB2, and acts on the plasma membrane in which it opens pores leading to ion leakage and cell death. The globular structure of bacteriocin AS-48 is composed of five alpha helices enclosing a hydrophobic core. The mammalian NK-lysin effector protein of T and natural killer cells has a similar structure, though it lacks sequence homology with bacteriocins AS-48.

<span class="mw-page-title-main">GSDMD</span> Protein-coding gene in the species Homo sapiens

Gasdermin D (GSDMD) is a protein that in humans is encoded by the GSDMD gene on chromosome 8. It belongs to the gasdermin family which is conserved among vertebrates and comprises six members in humans, GSDMA, GSDMB, GSDMC, GSDMD, GSDME (DFNA5) and DFNB59 (Pejvakin). Members of the gasdermin family are expressed in a variety of cell types including epithelial cells and immune cells. GSDMA, GSDMB, GSDMC, GSDMD and GSDME have been suggested to act as tumour suppressors.

Pyocins are bacteriocins produced by bacteria belonging to the Pseudomonas genus. François Jacob described the first pyocin in 1954. Pyocins can be divided into three distinct classes: S-type, R-type, and F-type pyocins. S-type pyocins are colicin-like bacteriocins as R-type and F-type pyocins belong to tailocins.

References

  1. ↑ Feldgarden M, Riley MA (1999). "The phenotypic and fitness effects of colicin resistance in Escherichia coli K-12". Evolution. 53 (4): 1019–27. doi:10.2307/2640807. JSTOR   2640807. PMID   28565527.
  2. ↑ Kang C, Postle K, Chen G, Park H, Youn B, Hilsenbeck JL (2004). "Crystal structure of the cytotoxic bacterial protein colicin B at 2.5 A resolution". Mol. Microbiol. 51 (3): 711–20. doi: 10.1111/j.1365-2958.2003.03884.x . PMID   14731273.
  3. ↑ Cramer WA, Zakharov SD, Antonenko YN, Kotova EA (2004). "On the role of lipid in colicin pore formation". Biochim. Biophys. Acta. 1666 (1): 239–49. doi: 10.1016/j.bbamem.2004.07.001 . PMID   15519318.
  4. ↑ Cascales et al. (2007). Colicin Biology. Microbio. and Mol. Bio. Rev. 71(1), 158-229. Abstract pdf
  5. 1 2 Wiener, Michael; Freymann, Douglas; Ghosh, Partho; Stroud, Robert M. (January 1997). "Crystal structure of colicin Ia". Nature. 385 (6615): 461–464. doi:10.1038/385461a0. ISSN   1476-4687.
  6. ↑ Cao Z, Klebba PE (2002). "Mechanisms of colicin binding and transport through outer membrane porins". Biochimie. 84 (5–6): 399–412. doi:10.1016/S0300-9084(02)01455-4. PMID   12423783.
  7. ↑ van den Elzen PJ, Gaastra W, Spelt CE, de Graaf FK, Veltkamp E, Nijkamp HJ (October 1980). "Molecular structure of the immunity gene and immunity protein of the bacteriocinogenic plasmid Clo DF13". Nucleic Acids Res. 8 (19): 4349–63. doi:10.1093/nar/8.19.4349. PMC   324244 . PMID   6253914.
  8. ↑ van den Elzen PJ, Veltkamp E, Nijkamp HJ, Walters HH (1983). "Molecular structure and function of the bacteriocin gene and bacteriocin protein of plasmid Clo DF13". Nucleic Acids Res. 11 (8): 2465–2477. doi:10.1093/nar/11.8.2465. PMC   325896 . PMID   6344017.
  9. ↑ Luria, S. E. (1969) Nobel Lecture
  10. ↑ Mader, Andreas; von Bronk, Benedikt; Ewald, Benedikt; Kesel, Sara; Schnetz, Karin; Frey, Erwin; Opitz, Madeleine (2015-03-09). "Amount of Colicin Release in Escherichia coli Is Regulated by Lysis Gene Expression of the Colicin E2 Operon". PLoS ONE. 10 (3): e0119124. doi:10.1371/journal.pone.0119124. ISSN   1932-6203. PMC   4353708 . PMID   25751274.
  11. ↑ "Kleanthous Research Group" . Retrieved 23 May 2017.
  12. ↑ Hammami R, Zouhir A, Ben Hamida J, Fliss I (2007). "BACTIBASE: a new web-accessible database for bacteriocin characterization". BMC Microbiology. 7: 89. doi:10.1186/1471-2180-7-89. PMC   2211298 . PMID   17941971.
  13. ↑ Hammami R, Zouhir A, Le Lay C, Ben Hamida J, Fliss I (2010). "BACTIBASE second release: a database and tool platform for bacteriocin characterization". BMC Microbiology. 10: 22. doi:10.1186/1471-2180-10-22. PMC   2824694 . PMID   20105292.
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