Biology:Rhs toxins
Rhs toxins belong to the polymorphic toxin category of bacterial exotoxins.[1] Rhs proteins are widespread and can be produced by both Gram-negative and Gram-positive bacteria.[2] Rhs toxins are very large proteins of usually more than 1,500 aminoacids with variable C-terminal toxic domains. Their toxic activity can either target eukaryotes or other bacteria.
Domain architecture
In their large N-terminal region, Rhs toxins comprise RHS/YD repeats in various number (PF05593) (RHS meaning Rearrangement Hot Spot) [3] and another "RHS-repeats associated core" domain (PF03527). In contrast, their C-terminal regions are shorter and harbor highly variable C-terminal domains including many domains with a predicted nuclease activity.[2]
Function
Anti-eukaryotic activity
These toxins encompass Rhs toxins of insect pathogens with an activity against insects.[4] This group also include Rhs toxins with an activity against human phagocytic cells that contribute to pathogenesis of Pseudomonas aeruginosa.[5]
Anti-bacterial activity
A role in inter-bacterial competition has been demonstrated for the plant pathogen Dickeya dadantii and for the human pathogen Escherichia coli.[6][7]
When a polymorphic toxin with anti-bacterial activity is produced by a bacterial strain, this strain is protected by a specific immunity protein encoded by a gene immediately downstream of the toxin gene.[1]
Delivery
Some Rhs toxins such as the previously mentioned system in Dickeya dadantii appear to be dependent on the type VI secretion system for delivery into neighbouring cells.[6] PAAR domain toxins such as Rhs appear to form the sharp tip of the type VI secretion system being attached to the VgrG of the secretion apparatus.[8] The C-terminal toxins of Rhs may vary to diversify the antimicrobial activity of the type VI secretion system.[7]
References
- ↑ 1.0 1.1 "New players in the toxin field: polymorphic toxin systems in bacteria". mBio 6 (3): e00285-15. May 2015. doi:10.1128/mBio.00285-15. PMID 25944858.
- ↑ 2.0 2.1 "Polymorphic toxin systems: Comprehensive characterization of trafficking modes, processing, mechanisms of action, immunity and ecology using comparative genomics". Biology Direct 7: 18. June 2012. doi:10.1186/1745-6150-7-18. PMID 22731697.
- ↑ "Rhs elements of Escherichia coli: a family of genetic composites each encoding a large mosaic protein". Molecular Microbiology 12 (6): 865–71. June 1994. doi:10.1111/j.1365-2958.1994.tb01074.x. PMID 7934896.
- ↑ "The BC component of ABC toxins is an RHS-repeat-containing protein encapsulation device". Nature 501 (7468): 547–50. September 2013. doi:10.1038/nature12465. PMID 23913273. http://espace.library.uq.edu.au/view/UQ:313861/Busby_Nature_2014_postrefereed.pdf.
- ↑ "An rhs gene of Pseudomonas aeruginosa encodes a virulence protein that activates the inflammasome". Proceedings of the National Academy of Sciences of the United States of America 109 (4): 1275–80. January 2012. doi:10.1073/pnas.1109285109. PMID 22232685.
- ↑ 6.0 6.1 "Rhs proteins from diverse bacteria mediate intercellular competition". Proceedings of the National Academy of Sciences of the United States of America 110 (17): 7032–7. April 2013. doi:10.1073/pnas.1300627110. PMID 23572593.
- ↑ 7.0 7.1 "PAAR-Rhs proteins harbor various C-terminal toxins to diversify the antibacterial pathways of type VI secretion systems". Environmental Microbiology 19 (1): 345–360. January 2017. doi:10.1111/1462-2920.13621. PMID 27871130.
- ↑ "PAAR-repeat proteins sharpen and diversify the type VI secretion system spike" (in En). Nature 500 (7462): 350–353. August 2013. doi:10.1038/nature12453. PMID 23925114. PMC 3792578. https://dash.harvard.edu/bitstream/handle/1/11879901/3792578.pdf?sequence=1.
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