Two Heads Are (Sometimes) Better Than One: How Rate Formulations Impact Molecular Motor Dynamics

TL;DR

This paper investigates how different rate formulations in stochastic models of molecular motor transport influence cargo movement, revealing that certain formulations can lead to counterintuitive behaviors like faster movement of loaded motor groups.

Contribution

It demonstrates that the choice of rate formulation significantly impacts motor dynamics, even under the same thermodynamic constraints, highlighting the importance of modeling assumptions.

Findings

Loaded motor groups can move faster than unloaded motors under certain rate formulations

Rate formulation choice affects cargo transport characteristics

Thermodynamic constraints do not uniquely determine motor behavior

Abstract

Cells are complex structures which require considerable amounts of organization via transport of large intracellular cargo. While passive diffusion is often sufficiently fast for the transport of smaller cargo, active transport is necessary to organize large structures on short timescales. The main mechanism of this transport is by cargo attachment to motors which walk in a directed fashion along intracellular filaments. There are a number of models which seek to describe the motion of motors with attached cargo, from detailed microscopic to coarse phenomenological descriptions. We focus on the intermediate-detailed discrete stochastic hopping models, and explore how cargo transport changes depending on the number of motors, motor interaction, system constraints and rate formulations which are derived from common thermodynamic assumptions. We find that, despite obeying the same detailed balance constraint, the choice of rate formulation considerably affects the characteristics of the overall motion of the system, with one rate formulation exhibiting novel behavior of loaded motor groups moving faster than a single unloaded motor.