Recombinant α-actin for specific fluorescent labeling

Until recently, actin was thought to act merely as a passive track for its motility partner, myosin, during actomyosin interactions. Yet a recent report having observed dynamical conformational changes in labeled skeletal muscle a-actin suggests that actin has a more active role. Because the labeling technique was still immature, however, conclusions regarding the signi-ficance of the different conformations are difficult to make. Here, we describe the preparation of fully active a-actin obtained from a baculovirus expression system. We developed a-actin recombinants, of which subdomains 1 and 2 have specific sites for fluorescent probes. This specific labeling technique offers to significantly expand the information acquired from actin studies.