Biochemical Studies of Myosin

This article describes methods for expressing and obtaining purified smooth muscle myosin subfragments using the baculovirus/insect cell expression system, as well as methods for purifying whole myosin from tissue. Protocols for several gel assays that are routinely used with myosin are given, including gels to monitor light chain phosphorylation state and native gels to determine protein homogeneity. Steady-state myosin ATPase and actin-activated ATPase determinations are described, as are some of the more basic transient-state kinetic parameters that can be measured. The in vitro motility assay, in which the rate of actin movement over myosin or its subfragments is quantified, is also presented.