MYOSIN-SPECIFIC ADAPTATIONS OF THE MOTILITY ASSAY

The ability to directly observe the behavior of single actin filaments as they are translocated by myosin has spawned a number of variations on the assay, which have contributed to a more detailed understanding of the molecular basis for the interaction of actin and myosin. This chapter presents myosin-specific adaptations of the motility assay. The motility assay is a quick and sensitive method to quantitate the interaction of myosin with actin. The motility assay is a versatile assay subject to many modifications depending on the system being studied. Some of the possible variations include assays with synthetic thick filaments, soluble myosin or its subfragments, native thick filaments, and smooth muscle and nonmuscle myosin II. The goal of most experiments, using the motility assay, is to quantitate the speed of actin filament sliding. This can be accomplished in several ways, such as by using a computer-assisted method for tracking moving objects or by using a virtually computer-driven method—the Expert Vision Motion Analysis System. © 1993, Elsevier Science Publishers, B.V.