Stall force does not affect the stalk coiling propagation of Vorticella convallaria

ABSTRACTMycoplasma mobileis a bacterium that uses a unique mechanism to glide on solid surfaces at a velocity of up to 4.5 µm/s. Its gliding machinery comprises hundreds of units that generate the force for gliding based on the energy derived from ATP; the units catch and pull on sialylated oligosaccharides fixed to solid surfaces. In the present study, we measured the stall force of wild-type and mutant strains ofM. mobilecarrying a bead manipulated using optical tweezers. The strains that had been enhanced for binding exhibited weaker stall forces than the wild-type strain, indicating that stall force is related to force generation rather than to binding. The stall force of the wild-type strain decreased linearly from 113 to 19 pN following the addition of 0–0.5 mM free sialyllactose (a sialylated oligosaccharide), with a decrease in the number of working units. Following the addition of 0.5 mM sialyllactose, the cells carrying a bead loaded using optical tweezers exhibited stepwise movements with force increments. The force increments ranged from 1 to 2 pN. Considering the 70-nm step size, this small unit force may be explained by the large gear ratio involved in theM. mobilegliding machinery.SIGNIFICANCEMycoplasmais a genus of bacteria that parasitizes animals. Dozens ofMycoplasmaspecies glide over the tissues of their hosts during infection. The gliding machinery ofMycoplasma mobile, the fastest species, includes intracellular motors and hundreds of legs on the cell surface. In the present study, we precisely measured force generation using a highly focused laser beam arrangement (referred to as optical tweezers) under various conditions. The measurements obtained in this study suggest that the rapid gliding exhibited byM. mobilearises from the large gear ratio of its gliding machinery.

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Correction for Blehm et al., In vivo optical trapping indicates kinesin’s stall force is reduced by dynein during intracellular transport

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1308350110 ◽

2013 ◽

Vol 110 (23) ◽

pp. 9613-9613 ◽

Cited By ~ 2

Keyword(s):

Intracellular Transport ◽

Optical Trapping ◽

Stall Force

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Detailed Analyses of Stall Force Generation in Mycoplasma mobile Gliding

Biophysical Journal ◽

10.1016/j.bpj.2018.01.029 ◽

2018 ◽

Vol 114 (6) ◽

pp. 1411-1419 ◽

Cited By ~ 8

Author(s):

Masaki Mizutani ◽

Isil Tulum ◽

Yoshiaki Kinosita ◽

Takayuki Nishizaka ◽

Makoto Miyata

Keyword(s):

Force Generation ◽

Stall Force

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Modeling meiotic chromosome pairing: increased fidelity from a tug of war between telomere forces and a pairing-based Brownian ratchet

10.1101/332767 ◽

2018 ◽

Author(s):

Wallace F. Marshall ◽

Jennifer C. Fung

Keyword(s):

Meiotic Chromosome ◽

Meiotic Pairing ◽

Dependent Manner ◽

Brownian Ratchet ◽

Lower Affinity ◽

Homolog Pairing ◽

High Affinity ◽

Random Forces ◽

Stall Force ◽

Do So

AbstractMeiotic homolog pairing involves associations between homologous DNA regions scattered along the length of a chromosome. When homologs associate, they tend to do so by a processive zippering processive, which apparently results from avidity effects. Using a computational model, we show that this avidity-driven processive zippering reduces the selectivity of pairing. When active random forces are applied to telomeres, this drop in selectivity is eliminated in a force-dependent manner. Further simulations suggest that active telomere forces are engaged in a tug-of-war against zippering, which can be interpreted as a Brownian ratchet with a stall force that depends on the dissociation constant of pairing. When perfectly homologous regions of high affinity compete with homeologous regions of lower affinity, the affinity difference can be amplified through this tug of war effect provided the telomere force acts in a range that is strong enough to oppose zippering of homeologs while still permitting zippering of correct homologs. The degree of unzippering depends on the radius of the nucleus, such that complete unzippering of homeologous regions can only take place if the nucleus is large enough to pull the two chromosomes completely apart. A picture of meiotic pairing thus emerges that is fundamentally mechanical in nature, possibly explaining the purpose of active telomere forces, increased nuclear diameter, and the presence of “Maverick” chromosomes in meiosis.

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The kinesin-8 Kip3 depolymerizes microtubules with a collective force-dependent mechanism

10.1101/844829 ◽

2019 ◽

Author(s):

Michael Bugiel ◽

Mayank Chugh ◽

Tobias Jörg Jachowski ◽

Erik Schäffer ◽

Anita Jannasch

Keyword(s):

Cell Division ◽

Optical Tweezers ◽

High Precision ◽

Residence Time ◽

Binding Activity ◽

Dependent Manner ◽

Microtubule Depolymerization ◽

Cellular Processes ◽

Length Changes ◽

Stall Force

ABSTRACTMicrotubules are highly dynamic filaments with dramatic structural rearrangements and length changes during the cell cycle. An accurate control of the microtubule length is essential for many cellular processes in particular, during cell division. Motor proteins from the kinesin-8 family depolymerize microtubules by interacting with their ends in a collective and length-dependent manner. However, it is still unclear how kinesin-8 depolymerizes microtubules. Here, we tracked the microtubule end-binding activity of yeast kinesin-8, Kip3, under varying loads and nucleotide conditions using high-precision optical tweezers. We found that single Kip3 motors spent up to 200 s at the microtubule end and were not stationary there but took several 8-nm forward and backward steps that were suppressed by loads. Interestingly, increased loads, similar to increased motor concentrations, also exponentially decreased the motors’ residence time at the microtubule end. On the microtubule lattice, loads also exponentially decreased the run length and time. However, for the same load, lattice run times were significantly longer compared to end residence times suggesting the presence of a distinct force-dependent detachment mechanism at the microtubule end. The force dependence of the end residence time enabled us to estimate what force must act on a single motor to achieve the microtubule depolymerization speed of a motor ensemble. This force is higher than the stall force of a single Kip3 motor, supporting a collective force-dependent depolymerization mechanism that unifies the so-called “bump-off” and “switching” models. Understanding the mechanics of kinesin-8’s microtubule end activity will provide important insights into cell division with implications for cancer research.STATEMENT OF SIGNIFICANCEKinesin-8 motors are important for microtubule length regulation and are over-expressed in different types of cancer. Yet, on the molecular level, it is unclear how these motors depolymerize microtubules. Using high-precision optical tweezers, we measured how single yeast kinesin-8 motors, Kip3, interacted with the microtubule end. Interestingly, we found that single Kip3 motors were still motile at the microtubule end. The force dependence of how long single motors were associated with the microtubule end enabled us to estimate what force motors must exert onto each other to achieve the collective microtubule depolymerization speed of many motors. Our data support a collective force-dependent depolymerization mechanism. A better understanding of Kip3’s microtubule end activity has implications for cell division and associated diseases.

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Force and Stepwise Movements of Gliding Motility in Human Pathogenic Bacterium Mycoplasma pneumoniae

Frontiers in Microbiology ◽

10.3389/fmicb.2021.747905 ◽

2021 ◽

Vol 12 ◽

Author(s):

Masaki Mizutani ◽

Yuya Sasajima ◽

Makoto Miyata

Keyword(s):

Optical Tweezers ◽

Mycoplasma Pneumoniae ◽

Binding Activity ◽

Gliding Motility ◽

Pathogenic Bacterium ◽

Step Size ◽

Bacterial Surface ◽

Human Pathogenic Bacterium ◽

A Cell ◽

Stall Force

Mycoplasma pneumoniae, a human pathogenic bacterium, binds to sialylated oligosaccharides and glides on host cell surfaces via a unique mechanism. Gliding motility is essential for initiating the infectious process. In the present study, we measured the stall force of an M. pneumoniae cell carrying a bead that was manipulated using optical tweezers on two strains. The stall forces of M129 and FH strains were averaged to be 23.7 and 19.7 pN, respectively, much weaker than those of other bacterial surface motilities. The binding activity and gliding speed of the M129 strain on sialylated oligosaccharides were eight and two times higher than those of the FH strain, respectively, showing that binding activity is not linked to gliding force. Gliding speed decreased when cell binding was reduced by addition of free sialylated oligosaccharides, indicating the existence of a drag force during gliding. We detected stepwise movements, likely caused by a single leg under 0.2-0.3 mM free sialylated oligosaccharides. A step size of 14-19 nm showed that 25-35 propulsion steps per second are required to achieve the usual gliding speed. The step size was reduced to less than half with the load applied using optical tweezers, showing that a 2.5 pN force from a cell is exerted on a leg. The work performed in this step was 16-30% of the free energy of the hydrolysis of ATP molecules, suggesting that this step is linked to the elementary process of M. pneumoniae gliding. We discuss a model to explain the gliding mechanism, based on the information currently available.

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Stall force of a cargo driven by N interacting motor proteins

EPL (Europhysics Letters) ◽

10.1209/0295-5075/117/28004 ◽

2017 ◽

Vol 117 (2) ◽

pp. 28004 ◽

Cited By ~ 1

Author(s):

Deepak Bhat ◽

Manoj Gopalakrishnan

Keyword(s):

Motor Proteins ◽

Stall Force

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Static Characterization of the Driving, Normal and Stall Forces of a Double-Sided Moving-Permanent Magnet-Type Planar Actuator Based on Orthogonal Planar Windings

Sensors ◽

10.3390/s18103526 ◽

2018 ◽

Vol 18 (10) ◽

pp. 3526

Author(s):

Marilia A. da Silveira ◽

Marcos J. Susin ◽

Aly F. Flores Filho ◽

David G. Dorrell

Keyword(s):

Permanent Magnet ◽

External Force ◽

Analytical Methods ◽

Permanent Magnets ◽

Magnetic Coupling ◽

Experimental Results ◽

Average Sensitivity ◽

Stall Force ◽

Numerical And Analytical Methods

This work presents a study of the traction, normal and stall forces in a two-sided planar actuator with orthogonal planar windings and a mover that comprises two cars magnetically coupled to each other through two pairs of permanent magnets (PMs). There is no ferromagnetic armature core because of the permanent magnets array in the mover and orthogonal traction forces can be generated in order to move both cars jointly in any direction on a plane. The stall force is the minimal force necessary to break up the magnetic coupling between the two cars. When one of the cars is subjected to an external force through the x- or y-axis, the cars can become out of alignment with respect to each other and the planar actuator cannot work properly. The behavior of the forces was modelled by numerical and analytical methods and experimental results were obtained from tests carried out on a prototype. The average sensitivity of the measured static propulsion planar force along either axis is 4.48 N/A. With a 20-mm displacement between the cars along the direction of the x-axis and no armature current, a magnetic stall force of 17.26 N is produced through the same axis in order to restore the alignment of the two cars

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Force production of human cytoplasmic dynein is limited by its processivity

Science Advances ◽

10.1126/sciadv.aaz4295 ◽

2020 ◽

Vol 6 (15) ◽

pp. eaaz4295 ◽

Cited By ~ 5

Author(s):

Sibylle Brenner ◽

Florian Berger ◽

Lu Rao ◽

Matthew P. Nicholas ◽

Arne Gennerich

Keyword(s):

Optical Tweezers ◽

Molecular Motor ◽

Force Production ◽

Cytoplasmic Dynein ◽

Force Generation ◽

New Paradigm ◽

Average Force ◽

Complex Motor ◽

Hyperbolic Curve ◽

Stall Force

Cytoplasmic dynein is a highly complex motor protein that generates forces toward the minus end of microtubules. Using optical tweezers, we demonstrate that the low processivity (ability to take multiple steps before dissociating) of human dynein limits its force generation due to premature microtubule dissociation. Using a high trap stiffness whereby the motor achieves greater force per step, we reveal that the motor’s true maximal force (“stall force”) is ~2 pN. Furthermore, an average force versus trap stiffness plot yields a hyperbolic curve that plateaus at the stall force. We derive an analytical equation that accurately describes this curve, predicting both stall force and zero-load processivity. This theoretical model describes the behavior of a kinesin motor under low-processivity conditions. Our work clarifies the true stall force and processivity of human dynein and provides a new paradigm for understanding and analyzing molecular motor force generation for weakly processive motors.

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