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Accueil > Research > VOULHOUX > Theme

Biology of type IV filamentous (Tff) nanomachines

- Insights into the type II secretion system (T2SS)

The type II secretion system (T2SS) is devoted to the secretion of large folded effectors. It is constituted by an outer membrane pore, the secretin and an inner membrane platform assembling a short type IV pilus-like structure called pseudopilus.

We are investigating the assembly and the functioning of the T2SSs in the model bacterium Pseudomonas aeruginosa.

We used various complementary protein-protein interaction experiments to reveal specific interactions between T2SS components and secreted effectors. This allows us to propose the first model of substrate recognition and transport by the Xcp T2SS (Douzi 2011). We further showed that two of those interactions trigger conformational changes into the assembly platform that may synchronize effector arrival and pseudopilus assembly

Recently, we settled an integrative structural biology approach to disclose the unexpected structural organization of the periplasmic domain of the secretin, XcpQN. Additional structure-based cysteine cross linking experiments demonstrated that secretin flexibility is mandatory for its function (Douzi, 2017).

- Characterization of a new metal uptake pathway mediated by the metallophore pseudopaline in Pseudomonas aeruginosa

Metal uptake is vital for all living organisms. In metal scarce conditions a common bacterial strategy consists in the biosynthesis of metallophores, their export in the extracellular medium and the recovery of a metal-metallophore complex through dedicated membrane transportersWe have characterized a four-gene operon in Pseudomonas aeruginosa involved in the biosynthesis and trafficking of a new metallophore named pseudopaline. In vivothe pseudopaline operon is regulated by

zinc through the Zur repressor. The pseudopaline system is involved in zinc uptake in metal scarce conditions mimicking a chelating environment (Lhospice, Gomez, Ouerdane et al, 2017). We are now looking for the missing transporters of the pseudopaline pathway and its involvement in Pseudomonas infections.