Membrane voltage-dependent activation of the flagellar protein export engine

Minamino, T.; Morimoto, Y. V.; Kinoshita, M.; Namba, K.

doi:10.1101/2020.07.18.210377

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bioRxiv · 10.1101/2020.07.18.210377

Membrane voltage-dependent activation of the flagellar protein export engine

Minamino, T.·Morimoto, Y. V.·Kinoshita, M.·Namba, K.

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Abstract

Ion motive force (IMF) consists of the electric potential difference ({Delta}{Psi}) and the ion concentration difference ({Delta}pI) across the cytoplasmic membrane. The flagellar protein export machinery is an ion/protein antiporter utilizing IMF to drive ion-coupled protein export, but it remains unknown how. Here, we report a {Delta}{Psi}-dependent activation mechanism of the transmembrane export gate complex. Depletions of both H+ and Na+ gradients nearly diminished flagellar protein export in the absence of the cytoplasmic ATPase complex, but an increase in {Delta}{Psi} by an upward shift of external pH from 7.5 to 8.5 dramatically recovered it. An increase in the cytoplasmic level of export substrates and gain-of-function mutations in FlhA enhanced protein export at external pH 7.5 in the absence of Na+ in a similar manner to {Delta}{Psi} increase. We propose that the export gate complex has a voltage-gated mechanism to activate the ion/protein antiporter of the flagellar protein export engine.

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Minamino, T., Morimoto, Y. V., Kinoshita, M., Namba, K.. 2020-07-18. Membrane voltage-dependent activation of the flagellar protein export engine. https://doi.org/10.1101/2020.07.18.210377

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