Chimeric adaptor proteins translocate diverse type VI secretion system effectors in Vibrio cholerae.

Vibrio cholerae is a diverse species of Gram-negative bacteria, commonly found in the aquatic environment and the causative agent of the potentially deadly disease cholera. These bacteria employ a type VI secretion system (T6 SS) when they encounter prokaryotic and eukaryotic competitors. This contractile puncturing device translocates a set of effector proteins into neighboring cells. Translocated effectors are toxic unless the targeted cell produces immunity proteins that bind and deactivate incoming effectors. Comparison of multiple V. cholerae strains indicates that effectors are encoded in T6 SS effector modules on mobile genetic elements. We identified a diverse group of chimeric T6 SS adaptor proteins required for the translocation of diverse effectors encoded in modules. An example for a T6 SS effector that requires T6 SS adaptor protein 1 (Tap-1) is TseL found in pandemic V. cholerae O1 serogroup strains and other clinical isolates. We propose a model in which Tap-1 is required for loading TseL onto the secretion apparatus. After T6 SS-mediated TseL export is completed, Tap-1 is retained in the bacterial cell to load other T6 SS machines. [ABSTRACT FROM AUTHOR]