Myosin V passing over Arp2/3 junctions: branching ratio calculated from the elastic lever arm model

TL;DR

This paper models myosin V's behavior at actin filament branches using an elastic lever arm model, predicting branching ratios that align with experimental data.

Contribution

It introduces a detailed elastic lever arm model to calculate branching probabilities of myosin V at actin junctions, providing quantitative predictions.

Findings

Predicted daughter filament branching ratio of 27%.

Predicted mother filament branching ratio of 73%.

Model aligns well with experimental observations.

Abstract

Myosin V is a two-headed processive motor protein that walks in a hand-over-hand fashion along actin filaments. When it encounters a filament branch, formed by the Arp2/3 complex, it can either stay on the straight mother filament, or switch to the daughter filament. We study both probabilities using the elastic lever arm model for myosin V. We calculate the shapes and bending energies of all relevant configurations in which the trail head is bound to the actin filament before Arp2/3 and the lead head is bound either to the mother or to the daughter filament. Based on the assumption that the probability for a head to bind to a certain actin subunit is proportional to the Boltzmann factor obtained from the elastic energy, we calculate the mother/daughter filament branching ratio. Our model predicts a value of 27% for the daughter and 73% for the mother filament. This result is in good agreement with recent experimental data.