Limits...
Cooperative protofilament switching emerges from inter-motor interference in multiple-motor transport.

Ando D, Mattson MK, Xu J, Gopinathan A - Sci Rep (2014)

Bottom Line: Within living cells, the transport of cargo is accomplished by groups of molecular motors.In contrast to kinesin's low sidestepping frequency when present as a single motor, with exactly two kinesins per cargo, we observed substantial motion perpendicular to the microtubule.Our model captures a surface-associated mode of kinesin, which is only accessible via inter-motor interference in groups, in which kinesin diffuses along the microtubule surface and rapidly "hops" between protofilaments without dissociating from the microtubule.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, University of California, Merced, CA, USA.

ABSTRACT
Within living cells, the transport of cargo is accomplished by groups of molecular motors. Such collective transport could utilize mechanisms which emerge from inter-motor interactions in ways that are yet to be fully understood. Here we combined experimental measurements of two-kinesin transport with a theoretical framework to investigate the functional ramifications of inter-motor interactions on individual motor function and collective cargo transport. In contrast to kinesin's low sidestepping frequency when present as a single motor, with exactly two kinesins per cargo, we observed substantial motion perpendicular to the microtubule. Our model captures a surface-associated mode of kinesin, which is only accessible via inter-motor interference in groups, in which kinesin diffuses along the microtubule surface and rapidly "hops" between protofilaments without dissociating from the microtubule. Critically, each kinesin transitions dynamically between the active stepping mode and this weak surface-associated mode enhancing local exploration of the microtubule surface, possibly enabling cellular cargos to overcome macromolecular crowding and to navigate obstacles along microtubule tracks without sacrificing overall travel distance.

Show MeSH

Related in: MedlinePlus

Experimental and Model Arrangements.(a) Our experimental setup consists of a 440-nm diameter polystyrene bead as the cargo (green), with two recombinant K560 half-height kinesins (blue, AE kinesin; red, SA kinesin) connected through C-terminal histidine tags to a single monoclonal antibody (dark blue). Below the motors is shown a 13-protofilament right-handed A-lattice microtubule39. The microtubule kinesin binding domain lattice is depicted; dark grey tubulins actively bind kinesin heads, while light grey tubulins interact through non-specific interactions. The transverse distance of 5.6 nm between microtubule protofilaments appears in red, and the axial spacing of 8 nm between kinesin binding locations appears in blue. (b) Transition rate variables and states in our dynamic two-motor state transition model.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4248269&req=5

f2: Experimental and Model Arrangements.(a) Our experimental setup consists of a 440-nm diameter polystyrene bead as the cargo (green), with two recombinant K560 half-height kinesins (blue, AE kinesin; red, SA kinesin) connected through C-terminal histidine tags to a single monoclonal antibody (dark blue). Below the motors is shown a 13-protofilament right-handed A-lattice microtubule39. The microtubule kinesin binding domain lattice is depicted; dark grey tubulins actively bind kinesin heads, while light grey tubulins interact through non-specific interactions. The transverse distance of 5.6 nm between microtubule protofilaments appears in red, and the axial spacing of 8 nm between kinesin binding locations appears in blue. (b) Transition rate variables and states in our dynamic two-motor state transition model.

Mentions: The experimental data for processivity and transverse displacement rate (Fig. 1, Xu et al19) are replicated by a generic kinesin transition rate model that includes the SA state and interference between motors. We explicitly simulate the two-motor system, dynamically modelling interference and the state of each motor throughout time; each motor can be in the AE state, the SA state, or the off state (completely unbound from the microtubule) (Fig. 2). The motors were considered to be permanently attached to the cargo bead but could change their state of attachment to the microtubule over time with seven transition rates and the state of the partner motor (Fig. 2B). We recorded the transverse and axial positions of the motors during the simulation with the axial position set by active ATP stepping of either motor and transverse displacements determined by the AE sidestepping rate and SA hopping rate (see Methods).


Cooperative protofilament switching emerges from inter-motor interference in multiple-motor transport.

Ando D, Mattson MK, Xu J, Gopinathan A - Sci Rep (2014)

Experimental and Model Arrangements.(a) Our experimental setup consists of a 440-nm diameter polystyrene bead as the cargo (green), with two recombinant K560 half-height kinesins (blue, AE kinesin; red, SA kinesin) connected through C-terminal histidine tags to a single monoclonal antibody (dark blue). Below the motors is shown a 13-protofilament right-handed A-lattice microtubule39. The microtubule kinesin binding domain lattice is depicted; dark grey tubulins actively bind kinesin heads, while light grey tubulins interact through non-specific interactions. The transverse distance of 5.6 nm between microtubule protofilaments appears in red, and the axial spacing of 8 nm between kinesin binding locations appears in blue. (b) Transition rate variables and states in our dynamic two-motor state transition model.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4248269&req=5

f2: Experimental and Model Arrangements.(a) Our experimental setup consists of a 440-nm diameter polystyrene bead as the cargo (green), with two recombinant K560 half-height kinesins (blue, AE kinesin; red, SA kinesin) connected through C-terminal histidine tags to a single monoclonal antibody (dark blue). Below the motors is shown a 13-protofilament right-handed A-lattice microtubule39. The microtubule kinesin binding domain lattice is depicted; dark grey tubulins actively bind kinesin heads, while light grey tubulins interact through non-specific interactions. The transverse distance of 5.6 nm between microtubule protofilaments appears in red, and the axial spacing of 8 nm between kinesin binding locations appears in blue. (b) Transition rate variables and states in our dynamic two-motor state transition model.
Mentions: The experimental data for processivity and transverse displacement rate (Fig. 1, Xu et al19) are replicated by a generic kinesin transition rate model that includes the SA state and interference between motors. We explicitly simulate the two-motor system, dynamically modelling interference and the state of each motor throughout time; each motor can be in the AE state, the SA state, or the off state (completely unbound from the microtubule) (Fig. 2). The motors were considered to be permanently attached to the cargo bead but could change their state of attachment to the microtubule over time with seven transition rates and the state of the partner motor (Fig. 2B). We recorded the transverse and axial positions of the motors during the simulation with the axial position set by active ATP stepping of either motor and transverse displacements determined by the AE sidestepping rate and SA hopping rate (see Methods).

Bottom Line: Within living cells, the transport of cargo is accomplished by groups of molecular motors.In contrast to kinesin's low sidestepping frequency when present as a single motor, with exactly two kinesins per cargo, we observed substantial motion perpendicular to the microtubule.Our model captures a surface-associated mode of kinesin, which is only accessible via inter-motor interference in groups, in which kinesin diffuses along the microtubule surface and rapidly "hops" between protofilaments without dissociating from the microtubule.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, University of California, Merced, CA, USA.

ABSTRACT
Within living cells, the transport of cargo is accomplished by groups of molecular motors. Such collective transport could utilize mechanisms which emerge from inter-motor interactions in ways that are yet to be fully understood. Here we combined experimental measurements of two-kinesin transport with a theoretical framework to investigate the functional ramifications of inter-motor interactions on individual motor function and collective cargo transport. In contrast to kinesin's low sidestepping frequency when present as a single motor, with exactly two kinesins per cargo, we observed substantial motion perpendicular to the microtubule. Our model captures a surface-associated mode of kinesin, which is only accessible via inter-motor interference in groups, in which kinesin diffuses along the microtubule surface and rapidly "hops" between protofilaments without dissociating from the microtubule. Critically, each kinesin transitions dynamically between the active stepping mode and this weak surface-associated mode enhancing local exploration of the microtubule surface, possibly enabling cellular cargos to overcome macromolecular crowding and to navigate obstacles along microtubule tracks without sacrificing overall travel distance.

Show MeSH
Related in: MedlinePlus