Non-exponential kinetics of unfolding under a constant force

Bell, Samuel; Terentjev, Eugene M.

doi:10.1063/1.4966922

Cited by 4 publications

(5 citation statements)

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“…The subunit, which is temporarily bound to the cavity, resists the filament movement, the www.nature.com/scientificreports www.nature.com/scientificreports/ associated counter-torque slowing down its natural rotation in the motor. The motor exerts an equal and opposite force on the substrate, helping it overcome the energy barrier and unfold (a number of studies give details of protein unfolding under force [42][43][44].…”

Section: Assisted Unfoldingmentioning

confidence: 99%

“…In the stall mode the rotation of the motor is fully blocked by the substrate which is able to apply G stall to the motor. This counter-torque builds up tension in the subunit protein, until it unfolds with the help of other mechanisms such as chaperones 1,4 , or just stochastically 43,44 . Mean first-passage time can be used to calculate the average time for such stochastic unfolding.…”

Section: Assisted Unfoldingmentioning

confidence: 99%

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FliI6-FliJ molecular motor assists with unfolding in the type III secretion export apparatus

Kucera

Terentjev

2020

Sci Rep

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flii 6-fliJ molecular motor assists with unfolding in the type iii secretion export apparatus Jiri Kucera & eugene M. terentjev ✉ the role of rotational molecular motors of the Atp synthase class is integral to the metabolism of cells. Yet the function of flii 6-fliJ complex, a homolog of the F 1 ATPase motor, within the flagellar export apparatus remains unclear. We use a simple two-state model adapted from studies of linear molecular motors to identify key features of this motor. the two states are the 'locked' ground state where the FliJ coiled coil filament experiences angular fluctuations in an asymmetric torsional potential, and a 'free' excited state in which FliJ undergoes rotational diffusion. Michaelis-Menten kinetics was used to treat transitions between these two states, and obtain the average angular velocity of the unloaded FliJ filament within the FliI 6 stator: ω max ≈ 9.0 rps. The motor was then studied under external counter torque conditions in order to ascertain its maximal power output: P max ≈ 42 k B T/s (or 102 kW/mol), and the stall torque: G stall ≈ 3 k B T/rad (or 0.01 nN•nm/rad). Two modes of action within the flagellar export apparatus are proposed, in which the motor performs useful work either by continuously 'grinding' through the resistive environment of the export gate, or by exerting equal and opposite stall force on it. In both cases, the resistance is provided by flagellin subunits entering the flagellar export channel prior to their unfolding. We therefore propose that the function of the flii 6-fliJ complex is to lower the energy barrier, and therefore assist in unfolding of the flagellar proteins before feeding them into the transport channel. With the advance of imaging techniques, our view of living matter and of its fundamental units, the cells, has changed dramatically. These micron-sized 'bags of chemicals' turned out to be run by complex yet physically describable networks of proteins, lipids, and carbohydrates. The immense number of processes occurring in a cell at any given moment would be unattainable in such a packed environment without a considerable level of organization and reaction catalysis. In general, this is achieved by proteins-long chains of amino acids that come in various sizes and shapes when folded in solution. Their functionality originates from polarity and hydrophobicity of different aminoacids, and is responsible for the unique self-assembly and the resulting properties that range from simple structural support to powerful catalysers. One such class of proteins are the molecular motors 1-3. These large molecular complexes are responsible for organised powered movement within cells and can be characterised by the following properties. They consume energy (usually chemical energy stored in molecules of ATP, or in electrochemical gradient of ions across membranes) and transform it into mechanical work. The energy input is crucial to drive the system out of equilibrium. Another requirement to achieve directed motion is the presence of asymmetry (or br...

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Section: Assisted Unfoldingmentioning

confidence: 99%

Section: Assisted Unfoldingmentioning

confidence: 99%

FliI6-FliJ molecular motor assists with unfolding in the type III secretion export apparatus

Kucera

Terentjev

2020

Sci Rep

Self Cite

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show abstract

“…The subunit, which is temporarily bound to the cavity, resists the filament movement, the associated counter-torque slowing down its natural rotation in the motor. The motor exerts an equal and opposite force on the substrate, helping it overcome the energy barrier and unfold (a number of studies give details of protein unfolding under force [43][44][45] ).…”

Section: Assisted Unfoldingmentioning

confidence: 99%

“…In the stall mode the rotation of the motor is fully suppressed by the substrate which is able to apply G stall to the motor. This counter-torque builds up tension in the subunit protein, until it unfolds with the help of other mechanisms such as chaperones 1,4 , or just stochastically 44,45 . Mean first-passage time can be used to calculate the average time for such stochastic unfolding.…”

Section: Assisted Unfoldingmentioning

confidence: 99%

FliI₆-FliJ molecular motor assists with unfolding in the type III secretion export apparatus

Kucera

Terentjev

2020

Preprint

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AbstractThe role of rotational molecular motors of the ATP synthase class is integral to the metabolism of cells. Yet the function of FliI6-FliJ complex - a homolog of the F1 ATPase motor - within the flagellar export apparatus remains unclear. We use a simple two-state model adapted from studies of linear molecular motors to identify key features of this motor. The two states are the ‘locked’ ground state where the FliJ coiled coil filament experiences fluctuations in an asymmetric torsional potential, and a ‘free’ excited state in which FliJ undergoes rotational diffusion. Michaelis-Menten kinetics was used to treat transitions between these two states, and obtain the average angular velocity of the FliJ filament within the FliI6 stator: ωmax ≈ 9.0 rps. The motor was then studied under external counter torque conditions in order to ascertain its maximal power output: Pmax ≈ 42 kBT/s, and the stall torque: Gstall ≈ 3 kBT/rad. Two modes of action within the flagellar export apparatus are proposed, in which the motor performs useful work either by continuously ‘grinding’ through the resistive environment, or by exerting equal and opposite stall force on it. In both cases, the resistance is provided by flagellin subunits entering the flagellar export channel prior to their unfolding. We therefore propose that the function of the FliI6-FliJ complex is to lower the energy barrier and therefore assist in unfolding of the flagellar proteins before feeding them into the transport channel.

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“…However, several studies have shown that the resulting empirical distributions did not follow the Poisson distributions ( Brujic et al., 2006 , 2007 ; Garcia-Manyes et al., 2007 ). This observation led to an effort to explain the measured deviation from exponentiality by means of static and dynamic disorders ( Kuo et al., 2010 ; Chatterjee and Cherayil, 2011 ; Zheng et al., 2014 ; Costescu et al., 2017 ; Kundu et al., 2020 ), corrugated energy landscapes ( Brujic et al., 2006 ; Lannon et al., 2012 ), and as consequence of the polymeric nature of the proteins ( Bell and Terentjev, 2016 ). In their pioneering computational work, Bura et al., showed how unfolding in polyproteins become less correlated when reducing the applied force from 88 to 66 pN ( Bura et al., 2007 , 2008 ).…”

Section: Introductionmentioning

confidence: 99%

Nonexponential kinetics captured in sequential unfolding of polyproteins over a range of loads

Chetrit

Sharma

Maayan

et al. 2022

Current Research in Structural Biology

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Non-exponential kinetics of unfolding under a constant force

Cited by 4 publications

References 30 publications

FliI6-FliJ molecular motor assists with unfolding in the type III secretion export apparatus

FliI6-FliJ molecular motor assists with unfolding in the type III secretion export apparatus

FliI₆-FliJ molecular motor assists with unfolding in the type III secretion export apparatus

Nonexponential kinetics captured in sequential unfolding of polyproteins over a range of loads

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