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Analysis of the toxic ADP-ribosyltransferase activity of an Rhs protein from Xenorhabdus bovienii SS-2004

par Dumont, Baptiste
Président du jury Vanhamme, Luc
Promoteur Van Melderen, Laurence
Publication Non publié, 2019-06-14

Thèse de doctorat

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Résumé :

Bacteria occupy an impressive diversity of environments in which complex networks of interactions shape the microbial communities’ relationships. In this context, an arsenal of bacterial nanoweapons have been selected to increase the relative fitness of each player. Some of these interactions depend on molecules diffused in the media whereas others rely on direct cell-to-cell contact. The type VI secretion system (T6SS) is one of those sophisticated ways to interact with neighboring cells. These supramolecular complexes allow Gram-negative bacteria to puncture the outer membrane of a cell in a contact- dependent manner and subsequently release a cocktail of toxins named effectors. Here we characterized RhsC, an effector of the Rhs family encoded in the Xenorhabdus bovienii SS-2004 genome. The carboxy-terminal domain of this Rhs toxin (RhsC-CT) shows a R-S-ExE catalytic motif characteristic of arginine ADP-ribosyltransferases. We demonstrated that this RhsC-CT uses the NAD+ coenzyme to ADP-ribosylate various protein targets in E. coli. The activity of this RhsC-CT toxin is inhibited via direct interaction with its cognate RhsIc immunity protein for which we obtained a structure.