Anomalous transport of subdiffusing cargos by single kinesin motors: the role of mechanochemical coupling and anharmonicity of tether

TL;DR

This study extends a model of kinesin-driven cargo transport in viscoelastic cytosol by incorporating mechanochemical coupling and tether anharmonicity, revealing enhanced efficiency and complex anomalous transport behaviors.

Contribution

It introduces a more realistic two-state model with mechanochemical coupling and tether anharmonicity, showing these factors increase thermodynamic efficiency and affect transport dynamics.

Findings

Normal and anomalous transport depend on binding potential and cargo size.

Maximal thermodynamic efficiency can reach about 50%.

Anomalously slow enzymatic turnovers occur in strongly anomalous regimes.

Abstract

Here we generalize our previous model of molecular motors trafficking subdiffusing cargos in viscoelastic cytosol by (i) including mechanochemical coupling between cyclic conformational fluctuations of the motor protein driven by the reaction of ATP hydrolysis and its translational motion within the simplest two-state model of hand-over-hand motion of kinesin, and also (ii) by taking into account the anharmonicity of the tether between the motor and cargo (its maximally possible extension length). It is shown that the major earlier results such as occurrence of normal versus anomalous transport depending on the amplitude of binding potential, cargo size and the motor turnover frequency not only survive in this more realistic model, but the results also look very similar for the correspondingly adjusted parameters. However, this more realistic model displays a substantially larger thermodynamic efficiency due to a bidirectional mechanochemical coupling. For realistic parameters, the maximal thermodynamic efficiency can be transiently about 50% as observed for kinesins, and even larger, surprisingly also in a novel strongly anomalous (sub)transport regime, where the motor enzymatic turnovers become also anomalously slow and cannot be characterized by a turnover rate. Here anomalously slow dynamics of the cargo enforces anomalously slow cyclic kinetics of the motor protein.