Function of the Vibrio PomB plug region based on the stator rotation model for bacterial flagellar motor

Homma, M.; Terashima, H.; Koiwa, H.; Kojima, S.

doi:10.1101/2021.03.16.435749

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bioRxiv · 10.1101/2021.03.16.435749

Function of the Vibrio PomB plug region based on the stator rotation model for bacterial flagellar motor

Homma, M.·Terashima, H.·Koiwa, H.·Kojima, S.

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Abstract

Bacterial flagella are the only real rotational motor organs in the biological world. The spiral-shaped flagellar filaments that extend from the cell surface rotate like a screw to create a propulsive force. The base of the flagellar filament has a protein motor consisting of a stator and a rotor embedded in the membrane. The motor part has stators composed of two types of membrane subunits, PomA(MotA) and PomB(MotB), which are energy converters coupled to the ion flow that assemble around the rotor. Recently, structures of the stator, in which two molecules of MotB stuck in the center of the MotA ring made of five molecules, were reported and a model in which the MotA ring rotates with respect to MotB, which is coupled to the influx of ions, was proposed. We focused on the Vibrio PomB plug region, which has been reported to control the activation of flagellar motors. We searched for the plug region, which is the interacting region, through site-directed photo-cross-linking and disulfide cross-linking experiments. Our results demonstrated that it interacts with the extracellular short loop region of PomA, which is between transmembrane 3 and 4. Although the motor halted following cross-linking, its function was recovered with a reducing reagent that disrupted the disulfide bond. Our results support the hypothesis, which has been inferred from the stator structure, that the plug region terminates the ion inflow by stopping the rotation of the rotor. ImportanceThe flagellar biological motor resembles a mechanical motor, which is composed of stator and rotor and where the rotational force is transmitted by gear-like movements. We hypothesized that the flagellar the rotation of stator that the pentamer of A subunits revolves around the axis of the B subunit dimer with ion flow. The plug region of the B subunit has been shown to regulate the ion flow. Herein, we demonstrated that the ion flow was terminated by the crosslinking between the plug region and the A subunit. These finding support the rotation hypothesis and explain the role of the plug region in terminating the rotation.

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Homma, M., Terashima, H., Koiwa, H., Kojima, S.. 2021-03-17. Function of the Vibrio PomB plug region based on the stator rotation model for bacterial flagellar motor. https://doi.org/10.1101/2021.03.16.435749

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