Competition and compensation: Dissecting the biophysical and functional differences between the class 3 myosin paralogs, myosins 3a and 3b

Stereocilia are actin protrusions with remarkably well-defined lengths and organization. A flurry of recent papers has reported multiple myosin motor proteins involved in regulating stereocilia structures by transporting actin-regulatory cargo to the tips of stereocilia.(1)(-)(13) In our recent paper, we show that two paralogous class 3 myosins — Myo3a and Myo3b — both transport the actin-regulatory protein Espin 1 (Esp1) to stereocilia and filopodia tips in a remarkably similar, albeit non-identical fashion.(1) Here we present experimental and computational data that suggests that subtle differences between these two proteins’ biophysical and biochemical properties can help us understand how these myosin species target and regulate the lengths of actin protrusions.