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.

This family belongs to the Lipase/Toxin Superfamily.



Dong, T.G., B.T. Ho, D.R. Yoder-Himes, and J.J. Mekalanos. (2013). Identification of T6SS-dependent effector and immunity proteins by Tn-seq in Vibrio cholerae. Proc. Natl. Acad. Sci. USA 110: 2623-2628.

Kamal, F., X. Liang, K. Manera, T.T. Pei, H. Kim, L.G. Lam, A. Pun, S.J. Hersch, and T.G. Dong. (2020). Differential Cellular Response to Translocated Toxic Effectors and Physical Penetration by the Type VI Secretion System. Cell Rep 31: 107766.

Liang, X., F. Kamal, T.T. Pei, P. Xu, J.J. Mekalanos, and T.G. Dong. (2019). An onboard checking mechanism ensures effector delivery of the type VI secretion system in. Proc. Natl. Acad. Sci. USA 116: 23292-23298.

Miyata, S.T., D. Unterweger, S.P. Rudko, and S. Pukatzki. (2013). Dual expression profile of type VI secretion system immunity genes protects pandemic Vibrio cholerae. PLoS Pathog 9: e1003752.

Unterweger, D., B. Kostiuk, R. Ă–tjengerdes, A. Wilton, L. Diaz-Satizabal, and S. Pukatzki. (2015). Chimeric adaptor proteins translocate diverse type VI secretion system effectors in Vibrio cholerae. EMBO. J. 34: 2198-2210.


TC#NameOrganismal TypeExample

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