Pyocin
Pyocins are bacteriocins produced by bacteria belonging to the Pseudomonas genus. François Jacob described the first pyocin in 1954.[1] 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.[2]
S-type pyocins
[edit]S-type (soluble) pyocins are binary protein complexes that compose of a cytotoxic protein and an immunity protein that protects the producing strain from cytotoxic effects. The amino-terminal domain of the protein takes part in receptor binding as the carboxy-terminal domain is responsible for cytotoxic effect. Most S-type pyocins act by degrading DNA and RNA but some exhibit their cytotoxicity by forming pores to cell surface or by lipid degradation. Several S-type pyocins have been found so far: S1, S2, AP41, S3, S4, S5, S6.[2]
Pyocin G is an example of a novel S1-type nuclease pyocin. It binds to hemin uptake receptor Hur on target cell surface and translocates to the cytoplasm where it degrades DNA. Pyocin G uses inner membrane proteins TonB1 and FtsH for translocation. Pyocin G is highly active against P.aeruginosa clinical isolates in vitro as well as in vivo and could be active in P.aeruginosa infections also in humans[3]
In silico methods are revealing also new types of S-pyocins when large databases of sequenced DNA from Pseudomonas-genus are being screened for new pyocin coding sequences.[2]
R-type and F-type pyocins
[edit]R- and F-type pyocins have been mainly investigated in P.aeruginosa. These two types differ by their structure; they are both composed of a sheath and a hollow tube forming a long helicoidal hexameric structure attached to a baseplate. There are multiple tail fibers that allow the particle to bind to the target cell. However, the R-pyocins are a large, rigid contractile tail-like structure whereas the F-pyocins are small flexible, non-contractile tail-like structures.[2]
To date five subgroups of R-type pyocins have been discovered: R1 to R5. F-type pyocins discovered so far are pyocin 28, 430f, F1, F2, and F3.[2]
References
[edit]- ^ Jacob, Francois. "Biosynthèse induite et mode d'action d'une pyocine, antibiotique de Pseudomonas pyocyanea". Ann. Inst. Pasteur. 86: 149–160.
- ^ a b c d e Ghequire, Maarten G.K.; De Mot, René (July 2014). "Ribosomally encoded antibacterial proteins and peptides from Pseudomonas". FEMS Microbiology Reviews. 38 (4): 523–568. doi:10.1111/1574-6976.12079. ISSN 1574-6976. PMID 24923764.
- ^ Atanaskovic, Iva; Mosbahi, Khedidja; Sharp, Connor; Housden, Nicholas G.; Kaminska, Renata; Walker, Daniel; Kleanthous, Colin (June 2020). "Targeted Killing of Pseudomonas aeruginosa by Pyocin G Occurs via the Hemin Transporter Hur". Journal of Molecular Biology. 432 (13): 3869–3880. doi:10.1016/j.jmb.2020.04.020. PMC 7322526. PMID 32339530.