Decoration of actin filaments with skeletal muscle heavy meromyosin containing either phosphorylated or dephosphorylated regulatory light chains.

Heavy meromyosin containing almost intact regulatory light chains (LC2) was obtained from monomeric phosphorylated and dephosphorylated rabbit fast skeletal muscle myosin by brief chymotryptic digestion in the presence of CaCl2. Actin filaments, complexed with heavy meromyosin, display two different forms of arrowhead, depending on the form of LC2.