Stable sub-complexes observed in situ suggest a modular assembly pathway of the bacterial flagellar motor

Kaplan, M.; Subramanian, P.; Ghosal, D.; Oikonomou, C. M.; Pirbadian, S.; Starwalt-Lee, R.; Gralnick, J. A.; El-Naggar, M. Y.; Jensen, G. J.

doi:10.1101/369405

bioRxiv · 10.1101/369405

Stable sub-complexes observed in situ suggest a modular assembly pathway of the bacterial flagellar motor

Kaplan, M.·Subramanian, P.·Ghosal, D.·Oikonomou, C. M.·Pirbadian, S.·Starwalt-Lee, R.·Gralnick, J. A.·El-Naggar, M. Y.·Jensen, G. J.

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Abstract

The self-assembly of cellular macromolecular machines such as the bacterial flagellar motor requires the spatio-temporal synchronization of gene expression, protein localization and association of a dozen or more unique components. In Salmonella and Escherichia coli, a sequential, outward assembly mechanism has been proposed for the flagellar motor starting from the inner membrane, with each subsequent component stabilizing the last. Here, using electron cryo-tomography of intact Legionella pneumophila, Pseudomonas aeruginosa and Shewanella oneidensis cells, we observe stable outer-membrane-embedded sub-complexes of the flagellar motor. These sub-complexes consist of the periplasmic embellished P- and L-rings, in the absence of other flagellar components, and bend the membrane inward dramatically. Additionally, we also observe independent inner-membrane sub-complexes consisting of the C- and MS-rings and export apparatus. These results suggest an alternate model for flagellar motor assembly in which outer- and inner-membrane-associated sub-complexes form independently and subsequently join, enabling later steps of flagellar production to proceed.

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Kaplan, M., Subramanian, P., Ghosal, D., Oikonomou, C. M., Pirbadian, S., Starwalt-Lee, R., Gralnick, J. A., El-Naggar, M. Y., Jensen, G. J.. 2018-07-14. Stable sub-complexes observed in situ suggest a modular assembly pathway of the bacterial flagellar motor. https://doi.org/10.1101/369405

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