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bioRxiv · 10.1101/2020.09.09.290478

The FlhA linker mediates flagellar protein export switching during flagellar assembly

Inoue, Y.·Kida, M.·Kinoshita, M.·Takekawa, N.·Namba, K.·Imada, K.·Minamino, T.
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Abstract

The flagellar protein export apparatus switches export specificity from hook-type to filament-type upon completion of hook assembly, thereby initiating filament assembly at the hook tip. The C-terminal cytoplasmic domain of FlhA (FlhAC) forms a homo-nonameric ring structure that serves as a docking platform for flagellar export chaperones in complex with their cognate filament-type substrates. Interactions of the flexible linker of FlhA (FlhAL) with its nearest FlhAC subunit in the ring allow the chaperones to bind to FlhAC to facilitate filament-type protein export, but it remains unclear how it occurs. Here, we report that FlhAL acts as a switch that brings the order to flagellar assembly. The crystal structure of FlhAC(E351A/D356A) showed that Trp-354 in FlhAL bound to the chaperone-binding site of its neighboring subunit. We propose that FlhAL binds to the chaperon-binding site of FlhAC to suppress the interaction between FlhAC and the chaperones until hook assembly is completed.

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Inoue, Y., Kida, M., Kinoshita, M., Takekawa, N., Namba, K., Imada, K., Minamino, T.. 2020-09-09. The FlhA linker mediates flagellar protein export switching during flagellar assembly. https://doi.org/10.1101/2020.09.09.290478

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