Speeds of actin translocation in vitro by myosins extracted from single rat muscle fibres of different types

As skeletal muscle fibres mostly express a single myosin isoform, they are a potential source of pure myosin isoforms. A technique is described that a llows extraction and identification of pure myosin isoforms from single fib res, and testing of such myosins in an in vitro motility assay (IVMA). The results show that the extraction procedure does not alter myosin function a nd support the view that single fibres are reliable sources of purified myo sin isoforms for IVMA.