dorsal/arxiv
View SchemaForce generation in small ensembles of Brownian motors
| Authors | Martin Linden, Tomi Tuohimaa, Ann-Beth Jonsson, Mats Wallin |
|---|---|
| Categories | |
| ArXiv ID | q-bio/0412026 |
| URL | https://arxiv.org/abs/q-bio/0412026 |
| DOI | 10.1103/PhysRevE.74.021908 |
| Journal | Phys. Rev. E 74 021908 (2006) |
Abstract
The motility of certain gram-negative bacteria is mediated by retraction of type IV pili surface filaments, which are essential for infectivity. The retraction is powered by a strong molecular motor protein, PilT, producing very high forces that can exceed 150 pN. The molecular details of the motor mechanism are still largely unknown, while other features have been identified, such as the ring-shaped protein structure of the PilT motor. The surprisingly high forces generated by the PilT system motivate a model investigation of the generation of large forces in molecular motors. We propose a simple model, involving a small ensemble of motor subunits interacting through the deformations on a circular backbone with finite stiffness. The model describes the motor subunits in terms of diffusing particles in an asymmetric, time-dependent binding potential (flashing ratchet potential), roughly corresponding to the ATP hydrolysis cycle. We compute force-velocity relations in a subset of the parameter space and explore how the maximum force (stall force) is determined by stiffness, binding strength, ensemble size, and degree of asymmetry. We identify two qualitatively different regimes of operation depending on the relation between ensemble size and asymmetry. In the transition between these two regimes, the stall force depends nonlinearly on the number of motor subunits. Compared to its constituents without interactions, we find higher efficiency and qualitatively different force-velocity relations. The model captures several of the qualitative features obtained in experiments on pilus retraction forces, such as roughly constant velocity at low applied forces and insensitivity in the stall force to changes in the ATP concentration.
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"abstract": "The motility of certain gram-negative bacteria is mediated by retraction of\ntype IV pili surface filaments, which are essential for infectivity. The\nretraction is powered by a strong molecular motor protein, PilT, producing very\nhigh forces that can exceed 150 pN. The molecular details of the motor\nmechanism are still largely unknown, while other features have been identified,\nsuch as the ring-shaped protein structure of the PilT motor. The surprisingly\nhigh forces generated by the PilT system motivate a model investigation of the\ngeneration of large forces in molecular motors. We propose a simple model,\ninvolving a small ensemble of motor subunits interacting through the\ndeformations on a circular backbone with finite stiffness. The model describes\nthe motor subunits in terms of diffusing particles in an asymmetric,\ntime-dependent binding potential (flashing ratchet potential), roughly\ncorresponding to the ATP hydrolysis cycle. We compute force-velocity relations\nin a subset of the parameter space and explore how the maximum force (stall\nforce) is determined by stiffness, binding strength, ensemble size, and degree\nof asymmetry. We identify two qualitatively different regimes of operation\ndepending on the relation between ensemble size and asymmetry. In the\ntransition between these two regimes, the stall force depends nonlinearly on\nthe number of motor subunits. Compared to its constituents without\ninteractions, we find higher efficiency and qualitatively different\nforce-velocity relations. The model captures several of the qualitative\nfeatures obtained in experiments on pilus retraction forces, such as roughly\nconstant velocity at low applied forces and insensitivity in the stall force to\nchanges in the ATP concentration.",
"arxiv_id": "q-bio/0412026",
"authors": [
"Martin Linden",
"Tomi Tuohimaa",
"Ann-Beth Jonsson",
"Mats Wallin"
],
"categories": [
"q-bio.SC",
"cond-mat.stat-mech",
"physics.bio-ph"
],
"doi": "10.1103/PhysRevE.74.021908",
"journal_ref": "Phys. Rev. E 74 021908 (2006)",
"title": "Force generation in small ensembles of Brownian motors",
"url": "https://arxiv.org/abs/q-bio/0412026"
},
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