1.C.132. The TseL Toxin (TseL) Family
Comparison of multiple Vibrio cholerae strains indicated that effectors are encoded in T6SS effector modules on mobile genetic elements. Unterweger et al. 2015 identified a diverse group of chimeric T6SS adaptor proteins required for the translocation of diverse effectors encoded in modules. An example for a T6SS effector that requires T6SS adaptor protein 1 (Tap-1) is TseL found in pandemic V. cholerae O1 serogroup strains and other clinical isolates. Unterweger et al. 2015 proposed a model in which Tap-1 is required for loading TseL onto the secretion apparatus. After T6SS-mediated TseL export is completed, Tap-1 is retained in the bacterial cell to load other T6SS machines. It acts on prokaryotic as well as eukaryotic target cells (Miyata et al. 2013; Dong et al. 2013). The TseL activity is not required for T6SS activity (Liang et al. 2019). TseL, but no other effectors or physical puncture, triggers a tit-for-tat response of P. aeruginosa H1-T6SS. Although E. coli is sensitive to all periplasmically expressed effectors, P. aeruginosa is most sensitive to TseL alone. Kamal et al. 2020 identified a number of stress response pathways that confer protection against TseL.
The TseL toxin of 641 aas and 1 or 2 central TMSs. See family description for properties.
TseL of Vibrio cholerae
Uncharacterized protein, probably a lipase, of 775 aas and from 0 to 4 possible TMSs.
UP of Spirodela intermedia
Uncharacterized protein, probable lipase, of 340 aas and 3 probable TMSs, one in the middle and two near the C-terminus of the protein.
UP of Momordica charantia (bitter melon)
Uncharacterized protein of 275 aas and possibly 2 TMSs.
UP of Paramecium sonneborni
Lipase domain protein, putative of 1867 aas and ~ 12 TMSs.
Lipase of Leishmania panamensis
Triacylglycerol lipase OBL1-like of 482 aas and ~ 7 TMSs in a 2 + 2 + 3 TMS arrangement.
Lipase of Hibiscus syriacus
Lipase family protein of 371 aas and one N-terminal TMS, with a second possible central TMS.
Lipase of Crateriforma spongiae