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A flagellum-specific chaperone facilitates assembly of the core type III export apparatus of the bacterial flagellum.
Fabiani, Florian D Renault, Thibaud T Peters, Britta Dietsche, Tobias Gálvez, Eric J C Guse, Alina Freier, Karen Charpentier, Emmanuelle Strowig, Till Franz-Wachtel, Mirita
Fabiani, Florian D
Renault, Thibaud T
Peters, Britta
Dietsche, Tobias
Gálvez, Eric J C
Guse, Alina
Freier, Karen
Charpentier, Emmanuelle
Strowig, Till
Franz-Wachtel, Mirita
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2017-08
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Abstract
Many bacteria move using a complex, self-assembling nanomachine, the bacterial flagellum. Biosynthesis of the flagellum depends on a flagellar-specific type III secretion system (T3SS), a protein export machine homologous to the export machinery of the virulence-associated injectisome. Six cytoplasmic (FliH/I/J/G/M/N) and seven integral-membrane proteins (FlhA/B FliF/O/P/Q/R) form the flagellar basal body and are involved in the transport of flagellar building blocks across the inner membrane in a proton motive force-dependent manner. However, how the large, multi-component transmembrane export gate complex assembles in a coordinated manner remains enigmatic. Specific for most flagellar T3SSs is the presence of FliO, a small bitopic membrane protein with a large cytoplasmic domain. The function of FliO is unknown, but homologs of FliO are found in >80% of all flagellated bacteria. Here, we demonstrate that FliO protects FliP from proteolytic degradation and promotes the formation of a stable FliP-FliR complex required for the assembly of a functional core export apparatus. We further reveal the subcellular localization of FliO by super-resolution microscopy and show that FliO is not part of the assembled flagellar basal body. In summary, our results suggest that FliO functions as a novel, flagellar T3SS-specific chaperone, which facilitates quality control and productive assembly of the core T3SS export machinery.
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A flagellum-specific chaperone facilitates assembly of the core type III export apparatus of the bacterial flagellum. 2017, 15 (8):e2002267 PLoS Biol.
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en
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1545-7885