8x2h

Structural highlights

Function

TCSL3_PARS9 Precursor of a cytotoxin that targets the vascular endothelium, inducing an anti-inflammatory effect and resulting in lethal toxic shock syndrome (PubMed:19527792, PubMed:21199912). TcsL constitutes the main toxin that mediates the pathology of P.sordellii infection, an anaerobic Gram-positive bacterium found in soil and in the gastrointestinal and vaginal tracts of animals and humans; although the majority of carriers are asymptomatic, pathogenic P.sordellii infections arise rapidly and are highly lethal (By similarity). This form constitutes the precursor of the toxin: it enters into host cells and mediates autoprocessing to release the active toxin (Glucosyltransferase TcsL) into the host cytosol (By similarity). Targets vascular endothelium by binding to the semaphorin proteins SEMA6A and SEMA6B, and enters host cells via clathrin-mediated endocytosis (By similarity). Once entered into host cells, acidification in the endosome promotes the membrane insertion of the translocation region and formation of a pore, leading to translocation of the GT44 and peptidase C80 domains across the endosomal membrane (By similarity) (PubMed:11500421). This activates the peptidase C80 domain and autocatalytic processing, releasing the N-terminal part (Glucosyltransferase TcsL), which constitutes the active part of the toxin, in the cytosol (By similarity).[UniProtKB:P18177][UniProtKB:Q46342]^{[1] [2] [3]} Active form of the toxin, which is released into the host cytosol following autoprocessing and inactivates small GTPases. Acts by mediating monoglucosylation of small GTPases of the Ras (H-Ras/HRAS, K-Ras/KRAS and N-Ras/NRAS) family in host cells at the conserved threonine residue located in the switch I region ('Thr-37/35'), using UDP-alpha-D-glucose as the sugar donor. Also able to catalyze monoglucosylation of some members of the Rho family (Rac1 and Rap2A), but with less efficiency than with Ras proteins. Monoglucosylation of host small GTPases completely prevents the recognition of the downstream effector, blocking the GTPases in their inactive form and leading to apoptosis. Induces an anti-inflammatory effect, mainly by inactivating Ras proteins which results in blockage of the cell cycle and killing of immune cells. The absence or moderate local inflammatory response allows C.sordellii spreading in deep tissues, production of toxin which is released in the general circulation and causes a toxic shock syndrome.[UniProtKB:Q46342]

References

1. ↑ Qa'Dan M, Spyres LM, Ballard JD. pH-enhanced cytopathic effects of Clostridium sordellii lethal toxin. Infect Immun. 2001 Sep;69(9):5487-93. PMID:11500421 doi:10.1128/IAI.69.9.5487-5493.2001
2. ↑ Hao Y, Senn T, Opp JS, Young VB, Thiele T, Srinivas G, Huang SK, Aronoff DM. Lethal toxin is a critical determinant of rapid mortality in rodent models of Clostridium sordellii endometritis. Anaerobe. 2010 Apr;16(2):155-60. PMID:19527792 doi:10.1016/j.anaerobe.2009.06.002
3. ↑ Carter GP, Awad MM, Hao Y, Thelen T, Bergin IL, Howarth PM, Seemann T, Rood JI, Aronoff DM, Lyras D. TcsL is an essential virulence factor in Clostridium sordellii ATCC 9714. Infect Immun. 2011 Mar;79(3):1025-32. PMID:21199912 doi:10.1128/IAI.00968-10