Impact of fluorescent protein fusions on the bacterial flagellar motor

Heo, Minyoung; Nord, Ashley L.; Chamousset, Delphine; Rijn, Erwin van; Beaumont, Bertus J. E.; Pedaci, Francesco

doi:10.1101/152595

Cited by 2 publications

(2 citation statements)

References 63 publications

(70 reference statements)

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“…However, this study was performed with stator units fused to a fluorescent protein, which can cause different behaviors from their wild type counterparts. 17,55 The current study is the first, to our knowledge, to report on the dynamics of wild type stator units in otherwise unperturbed motors.…”

Section: Discussionmentioning

confidence: 87%

A catch-bond drives stator mechanosensitivity in the Bacterial Flagellar Motor

Nord

Gachon

Pérez-Carrasco

et al. 2017

Preprint

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The bacterial flagellar motor (BFM) is the rotary motor which powers the swimming and swarming of many motile bacteria. The torque is provided by stator units, ion motive force powered ion channels known to assemble and disassemble dynamically in the BFM. This turnover is mechano-sensitive, with the number of engaged units dependent upon the viscous load experienced by the motor through the flagellum. However, the molecular mechanism driving BFM mechano-sensitivity is unknown. Here we directly measure the kinetics of arrival and departure of the stator units in individual wild-type motors via analysis of high-resolution recordings of motor speed, while dynamically varying the load on the motor via external magnetic torque. Obtaining the real-time stator stoichiometry before and after periods of forced motor stall, we measure both the number of active stator units at steady-state as a function of the load and the kinetic association and dissociation rates, by fitting the data to a reversible random sequential adsorption model. Our measurements indicate that BFM mechano-sensing relies on the dissociation rate of the stator units, which decreases with increasing load, while their association rate remains constant. This implies that the lifetime of an active stator unit assembled within the BFM increases when a higher force is applied to its anchoring point in the cell wall, providing strong evidence that a catch-bond mechanism can explain the mechano-sensitivity of the BFM.

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Section: Discussionmentioning

confidence: 87%

A catch-bond drives stator mechanosensitivity in the Bacterial Flagellar Motor

Nord

Gachon

Pérez-Carrasco

et al. 2017

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…A previous measurement of k off (10), performed on immobilized cells where motors were presumably stalled via the attachment of flagella to the coverslip, reported a value two orders of magnitude faster than our measured k off (γ1300). However, this study was performed with stator units fused to a fluorescent protein, which can cause different behaviors from their wild-type counterparts (10,41). The present study reports on the dynamics of wild-type stator units in otherwise unperturbed motors.…”

Section: Discussionmentioning

confidence: 99%

A Catch-Bond Drives Stator Mechanosensitivity in the Bacterial Flagellar Motor

Nord

Gachon

Pérez-Carrasco

et al. 2018

Biophysical Journal

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The bacterial flagellar motor (BFM) is the rotary motor that rotates each bacterial flagellum, powering the swimming and swarming of many motile bacteria. The torque is provided by stator units, ion motive force-powered ion channels known to assemble and disassemble dynamically in the BFM. This turnover is mechanosensitive, with the number of engaged units dependent on the viscous load experienced by the motor through the flagellum. However, the molecular mechanism driving BFM mechanosensitivity is unknown. Here, we directly measure the kinetics of arrival and departure of the stator units in individual motors via analysis of high-resolution recordings of motor speed, while dynamically varying the load on the motor via external magnetic torque. The kinetic rates obtained, robust with respect to the details of the applied adsorption model, indicate that the lifetime of an assembled stator unit increases when a higher force is applied to its anchoring point in the cell wall. This provides strong evidence that a catch bond (a bond strengthened instead of weakened by force) drives mechanosensitivity of the flagellar motor complex. These results add the BFM to a short, but growing, list of systems demonstrating catch bonds, suggesting that this "molecular strategy" is a widespread mechanism to sense and respond to mechanical stress. We propose that force-enhanced stator adhesion allows the cell to adapt to a heterogeneous environmental viscosity and may ultimately play a role in surface-sensing during swarming and biofilm formation.bacterial flagellar motor | molecular motor | mechanosensitivity | catch bond | Escherichia coli T he bacterial flagellar motor (BFM) is a large molecular complex found in many species of motile bacteria which actively rotates each flagellum of the cell, enabling swimming, chemotaxis, and swarming (1, 2). The rotor of the BFM is embedded within and spans the cellular membranes, coupling rotation to the extracellular hook and flagellar filament. Multiple transmembrane complexes, called stator units, are anchored around the perimeter of the rotor and bound to the rigid peptidoglycan (PG) layer (3-5). By harnessing the ion motive force, the stator units are responsible for torque generation, acting upon the common ring formed by FliG proteins on the cytosolic side of the rotor (Fig. 1A) (6, 7).Several studies have revealed the continuous exchange of various BFM molecular constituents (8-10), demonstrating that a static model for the BFM structure is not adequate. A prime example, and in contrast to macroscopic rotary motors, the stator of the BFM is dynamic; while each bound stator unit acts upon the rotor independently (11, 12), their stoichiometry in the motor varies. Once anchored around the rotor, stator units dynamically turn over, eventually diffusing away in the inner membrane (10). Each additional recruited stator unit increases the total torque and thus the measured rotational speed of the motor (11, 13), and up to 11 units have been observed to engage in an individual motor in Esche...

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Impact of fluorescent protein fusions on the bacterial flagellar motor

Abstract: bias-dependent asymmetry in the speed attained in the two rotation directions. 16All these effects could be mitigated by the insertion of a linker at the fusion point.

Cited by 2 publications

References 63 publications

A catch-bond drives stator mechanosensitivity in the Bacterial Flagellar Motor

A catch-bond drives stator mechanosensitivity in the Bacterial Flagellar Motor

A Catch-Bond Drives Stator Mechanosensitivity in the Bacterial Flagellar Motor

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