Inside cells, cargos such as vesicles URLanelles are transported by molecular motors to their correct locations via active motion on microtubule tracks and passive, Brownian diffusion. During the transportation of cargos, motor-cargo complexes (MCC) navigate the confining and crowded environment of the cytoskeletal network  . Motivated by this, we study a minimal two-state model of motor-driven cargo transport in confinement and predict transport properties that can be tested in experiments. We assume that the motion of the motor is directly affected by the entropic barrier due to confinement when it is in the passive, unbound state, but not in the active, bound state . Confinement can further modulate the motor's binding kinetics. We construct a lattice model based on a Fokker Planck description of the two-state system, and study it using a kinetic Monte Carlo method . We compute transport properties such as the average velocity and the effective diffusivity of the MCC. For constant binding and unbinding rates, we find that introducing confinement effectively enhances the unbinding rate and thereby reduces the motor processivity, leading to smaller effective diffusivity and average velocity . For spatially varying binding rates that depend on confinement, the average velocity is further reduced when the average binding rate is equal to the constant binding rate without confinement. However, confinement may lead to an enhancement in the average velocity if it results in a greater average binding rate than in the absence of confinement .
Inside cells, cargos such as vesicles URLanelles are transported by molecular motors to their correct locations via active motion on cytoskeletal tracks and passive, Brownian diffusion. During the transportation of cargos, motor-cargo complexes (MCC) navigate the confining and crowded environment of the cytoskeletal network and other macromolecules . Motivated by this, we study a minimal two-state model of motor-driven cargo transport in confinement and predict transport properties that can be tested in experiments. We assume that the motion of the MCC is directly affected by the entropic barrier due to confinement if it is in the passive, unbound state, but not in the active, bound state where it moves with a constant bound velocity. We construct a lattice model based on a Fokker Planck description of the two-state system, study it using a kinetic Monte Carlo method and compare our numerical results with analytical expressions for a mean field limit. We find that the effect of confinement strongly depends on the bound velocity and the binding kinetics of the MCC. Confinement effectively reduces the effective diffusivity and average velocity , except when it results in an enhanced average binding rate and thereby leads to a larger average velocity than when unconfined .
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microtubule
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and other macromolecules
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motor
MCC
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when
if
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. Confinement can further modulate the motor's binding kinetics.
where it moves with a constant bound velocity.
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and
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. We compute transport properties such as the average
and compare our numerical results with analytical expressions for a mean field limit. We find that the effect of confinement strongly depends on the bound
R
effective diffusivity
binding kinetics
R
For constant binding and unbinding rates, we find that introducing confinement effectively enhances the unbinding rate and thereby reduces the motor processivity, leading to smaller
Confinement effectively reduces the
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. For spatially varying binding rates that depend on confinement, the average velocity is further reduced when the average binding rate is equal to the constant binding rate without confinement. However, confinement may lead to an enhancement in the average velocity if
, except when
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a greater
an enhanced
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than in the absence of confinement
and thereby leads to a larger average velocity than when unconfined