In vitro assays of processive myosin motors

Myosin V is an actin-based motor thought to be involved in vesicle transpor t. Since the properties of such a motor may be expected to differ from thos e of muscle myosin II, we have examined myosin V-driven movement using a co mbination of gliding filament and optical trap assays to observe single mol ecules with high resolution. The results clearly demonstrate that brain: my osin V is a highly efficient processive motor. In vitro motility assays at law myosin V densities reveal apparent single-molecule supported movement. Processive stepping was also observed in optical trapping assays of myosin V-driven motion. Here the methods that were used to demonstrate the process ivity of myosin V are described. These methods include density-dependent as says that eliminate the possibility of aggregation or chance colocalization of multiple motors being responsible for apparent single-molecule motility . Such assays will be useful tools far identifying other processive classes of myosins. (C) 2000 Academic Press.