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1.C.130.  The Membrane Potential-dispersing Orphan 10 Toxin, (OrtT) Family

OrtT (YdcX), of 57 aas and 2 TMSs, is important for maintaining cell fitness during stress related to the stringent response (decreased amino acid, purine and thymidine availability). Overexpression inhibits cell growth, increases the formation of persister cells, and causes 99.9% of cells to undergo bacterial lysis within 2 hours after induction. Nucleoids condense, the cytoplasm seems empty and the periplasmic space enlarges. The intracellular ATP level decreases about 30-fold suggesting that the membrane potential may be disrupted (Islam et al. 2015). Although this protein is homologous to GhoT, the toxic component of a type IV toxin-antitoxin system, no antitoxin has been found. GhoS (the antitoxin for GhoT), YdcY (the neighboring gene), 5'- and 3'-UTRs as well as approximately 620 bp lengths of the BW25113 genome DNA were tested (Islam et al. 2015). The C-terminal (CT) toxin domains of contact-dependent growth inhibition (CDI) CdiA proteins target Gram-negative bacteria and must breach both the outer and inner membranes of target cells to exert growth inhibitory activity. It crosses the inner membrane via the SecY general secretory pathway (3.A.5.1.1) (Jones et al. 2021).


References associated with 1.C.130 family:

Cheng, H.Y., V.W. Soo, S. Islam, M.J. McAnulty, M.J. Benedik, and T.K. Wood. (2014). Toxin GhoT of the GhoT/GhoS toxin/antitoxin system damages the cell membrane to reduce adenosine triphosphate and to reduce growth under stress. Environ Microbiol 16: 1741-1754. 24373067
Islam, S., M.J. Benedik, and T.K. Wood. (2015). Orphan toxin OrtT (YdcX) of Escherichia coli reduces growth during the stringent response. Toxins (Basel) 7: 299-321. 25643179
Jones, A.M., P. Virtanen, D. Hammarlöf, W.J. Allen, I. Collinson, C.S. Hayes, D.A. Low, and S. Koskiniemi. (2021). Genetic Evidence for SecY Translocon-Mediated Import of Two Contact-Dependent Growth Inhibition (CDI) Toxins. mBio 12:. 33531386
Wang, X., D.M. Lord, H.Y. Cheng, D.O. Osbourne, S.H. Hong, V. Sanchez-Torres, C. Quiroga, K. Zheng, T. Herrmann, W. Peti, M.J. Benedik, R. Page, and T.K. Wood. (2012). A new type V toxin-antitoxin system where mRNA for toxin GhoT is cleaved by antitoxin GhoS. Nat Chem Biol 8: 855-861. 22941047