Biology:Streptolysin
| Streptolysin O | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Organism | |||||||
| Symbol | slo | ||||||
| UniProt | P0C0I3 | ||||||
| |||||||
| Streptolysin S | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Organism | |||||||
| Symbol | sagA | ||||||
| UniProt | Q1J7I0 | ||||||
| |||||||
Streptolysins are two hemolytic exotoxins from Streptococcus pyogenes.[1][2] Types include streptolysin O (SLO; slo), which is oxygen-labile, and streptolysin S (SLS; sagA), which is oxygen-stable.[3]
SLO is part of the thiol-activated cytolysin family.[4] It is hemolytically active only in a reversibly reduced state. It is antigenic, so its antibody antistreptolysin O can be detected in an antistreptolysin O titre.
SLS is stable in the presence of oxygen. It is not antigenic due to its small size. It is sometimes considered a bacteriocin due to similarities in the synthesis pathway.[5]
Streptolysin O
Streptolysin O (SLO; slo), is a bacterial toxin that has four protein domains which is known to make the plasma membranes in animal cells permeable. It does this by creating pore complexes within the membrane by first binding a monomer to the cholesterol found in the target membrane and then forming an oligomeric transmembrane pore.[6] This toxin excreted by a Gram-positive bacteria Streptococcus pyogenes, under the classification of Thiol-activated cytolysin or CDCs. In order for Streptolysin O to work effectively, it needs a significant amount of cholesterol to be present in the target membrane. Unlike other Cholesterol-dependent cytolysins, SLO contains a 60 Amino acid N-terminal domain that makes it easier to identify.
Human serum albumin has been demonstrated to neutralize the cytotoxic and hemolytic effects of SLO through its binding in a non-conventional site located in domain II, previously reported to interact also with C. difficile toxins.[7]
This toxin contains highly antigenic effects which causes it to produce the antibody anti-streptolysin O. Clinically, the presence of these antibodies can indicate a recent Group A streptococcal infection. Streptolysin O is also known to facilitate apoptosis in Keratinocytes. It is able to do this by translocating NAD+ glycohydrolase (SPN) across the target cells membrane. It then removes the N-terminal domain which stops SPN translocation leading to SPN mediated apoptosis.[8]
Group A Streptococcus infections
Group A streptococcal infections are responsible for 517,000 deaths annually across the world. Not much is known about the exact mechanism of action in natural infections however, once the infection is present within the cells it can cause devastating effects. When tested in human endometrium cells, 50% of the cells were killed within the first two hours as a result of processes stimulated by Streptolysin O and SpeB proteases. It has also been observed that both Steptolysin O and SpeB protease limit the innate immune response.[9]
Streptolysin S
Streptolysin S (SLS; sagA), is a cytolytic virulence factor which is a member of the thiazole/oxadole-modified microcin (TOMM) family. This cytolysin is a post-translationally modified peptide was synthesized through a natural evolutionary pathway. SLS is responsible for Streptococcus pyogenes' β-hemolytic appearance when grown on blood agar plates. Its biosynthesis is not fully known however, it is a critical virulence factor for Streptococcus pyogenes infections.[10] SLS brings about its virulence by damaging soft tissue and it can also act as a signaling molecule. When introduced to a host it will affect its phagocytes and also help to introduce GAS across the skin barrier.[11]
References
- ↑ "streptolysin" at Dorland's Medical Dictionary
- ↑ Streptolysin at the US National Library of Medicine Medical Subject Headings (MeSH)
- ↑ "Cytotoxic effects of streptolysin o and streptolysin s enhance the virulence of poorly encapsulated group a streptococci". Infection and Immunity 71 (1): 446–55. January 2003. doi:10.1128/IAI.71.1.446-455.2003. PMID 12496195.
- ↑ "Thiol-activated cytolysins: structure, function and role in pathogenesis". FEMS Microbiology Letters 182 (2): 197–205. January 2000. doi:10.1111/j.1574-6968.2000.tb08895.x. PMID 10620666.
- ↑ "Discovery of a widely distributed toxin biosynthetic gene cluster". Proceedings of the National Academy of Sciences of the United States of America 105 (15): 5879–84. April 2008. doi:10.1073/pnas.0801338105. PMID 18375757.
- ↑ "Streptolysin O: inhibition of the conformational change during membrane binding of the monomer prevents oligomerization and pore formation". Biochemistry 38 (46): 15204–11. November 1999. doi:10.1021/bi991678y. PMID 10563803.
- ↑ "Human Serum Albumin Binds Streptolysin O (SLO) Toxin Produced by Group A Streptococcus and Inhibits Its Cytotoxic and Hemolytic Effects". Frontiers in Immunology 11: 507092. 2020-12-08. doi:10.3389/fimmu.2020.507092. PMID 33363530.
- ↑ "Streptococcus pyogenes". Molecular Medical Microbiology. Elsevier. 2015. pp. 675–716. doi:10.1016/b978-0-12-397169-2.00038-x. ISBN 978-0-12-397169-2.
- ↑ "Streptococcus pyogenes infects human endometrium by limiting the innate immune response". The Journal of Clinical Investigation 131 (4). February 2021. doi:10.1172/jci130746. PMID 33320843.
- ↑ "HIV protease inhibitors block streptolysin S production". ACS Chemical Biology 10 (5): 1217–26. May 2015. doi:10.1021/cb500843r. PMID 25668590.
- ↑ "Streptolysin S-like virulence factors: the continuing sagA". Nature Reviews. Microbiology 9 (9): 670–81. August 2011. doi:10.1038/nrmicro2624. PMID 21822292.
 |  |
