Myosin from Abdominal Flexor Muscle in a Crayfish, Procambarus clarki Girard

Abstract

1. Crayfish (Procambarus clarki) myosin was obtained from abdominal flexor muscle. The Ca²⁺-ATPase activity of crayfish myosin was much lower than that of rabbit skeletal myosin. However, F-actin-activated Mg²⁺-ATPase of crayfish and its superprecipitation closely resembled those of rabbit skeletal myosin. This fact suggests that the ability of crayfish myosin to combine with F-actin is essentially the same as that of skeletal myosin, although the chemical structures of both the myosin molecules when involved in their Ca²⁺-ATPase activity must be different from each other.
2. Crayfish and rabbit skeletal myosins were subjected to SDS-polyacrylamide gel electrophoresis. Crayfish myosin was found to have one heavy chain and two distinct light chain components (CF-g1 and CF-g2), which have molecular weights of 18, 000 and 16, 000, respectively. These light chains correspond in molecular weight to the light chains (SK-g2 and SK-g3) in rabbit skeletal myosin.
3. CF-gl could be liberated from the crayfish myosin molecule reacting with 5, 5'-dithio-bis (2-nitrobenzoic acid), (Nbs₂), without recovery of ATPase activity by the addition of DTT. These properties are equivalent to those of SK-g₂ in rabbit skeletal myosin, although Nbs₂-treated crayfish myosin did not recover its ATPase activity at all.