Abstract
The interaction of porcine skeletal muscle actin filaments with 2 actin-associated proteins, .alpha.-actinin and vinculin (Mr [molecular raho] 130,000 protein), was studied in vitro with viscometry and light microscopy and EM. Vinculin, like .alpha.-actinin, binds of F-actin. The 2 proteins have different effects on the formation of filament networks: .alpha.-actinin crosslinks individual filaments in a manner strongly dependent on temperature and acts as a spacer. Vinculin forms actin bundles that display a paracrystalline substructure. In viscometric assays, .alpha.-actinin mimics the effects of actin gelation factors and vinculin acts as a gelation inhibitor. Complementary functions of these proteins in the regulation of cellular mobility are implied.