Influence of the passenger domain of a model autotransporter on the properties of its translocator domain |
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Authors: | Emmanuelle Dé Nathalie Saint Karine Glinel Albano C Meli Daniel Lévy Françoise Jacob-Dubuisson |
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Institution: | 1. UMR 6522 CNRS, PBM, Plate-forme Protéomique IFRMP23, Université de Rouen, Mont-Saint-Aignan cedex, Franceemmanuelle.de@univ-rouen.fr;3. INSERM U554 F34090 Montpellier, France;4. CNRS UMR 5048, Centre de Biochimie Structurale, Université Montpellier 1 et 2, Montpellier, France;5. UMR 6522 CNRS, PBM, Plate-forme Protéomique IFRMP23, Université de Rouen, Mont-Saint-Aignan cedex, France;6. Laboratoire Physico-Chimie, UMR 168 CNRS/Institut Curie, Paris, France;7. INSERM U629, Institut Pasteur de Lille, IFR142, Lille, France |
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Abstract: | Autotransporters are a superfamily of proteins secreted by Gram-negative bacteria including many virulence factors. They are modular proteins composed of an N-terminal signal peptide, a surface-exposed ‘passenger’ domain carrying the activity of the protein, and a C-terminal ‘translocator’ domain composed of an α-helical linker region and a transmembrane β-barrel. The translocator domain plays an essential role for the secretion of the passenger domain across the outer membrane; however, the mechanism of autotransport remains poorly understood. The whooping cough agent Bordetella pertussis produces an autotransporter serine-protease, SphB1, which is involved in the maturation of an adhesin at the bacterial surface. SphB1 also mediates the proteolytic maturation of its own precursor. We used SphB1 as a model autotransporter and performed the first comparisons of the biochemical and biophysical properties of an isolated translocator domain with those of the same domain preceded by the C-terminal moiety of its natural passenger. By using cross-linking and dynamic light scattering, we provide evidence that the passenger domain promotes the auto-association of SphB1, although these interactions appear rather labile. Electrophysiological studies revealed that the passenger domain of the autotransporter appears to maintain the translocator channel in a low-conductance conformation, most likely by stabilizing the α-helix inside the pore. That the passenger may significantly influence AT physicochemical properties is likely to be relevant for the in vivo maturation and stability of AT proteins. |
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Keywords: | Autotransporter SphB1 protein Bordetella pertussis passenger domain protein secretion |
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