  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.
