CHARACTERIZATION OF MYOSIN AND PARAMYOSIN FROM CRAYFISH FAST AND SLOWMUSCLES

Myosin and paramyosin were purified to homogeneity from deep abdominal flexor and extensor, and claw closer and opener muscles of crayfish. Myosins from fast muscle (deep abdominal flexor and extensor) consiste d of one species of heavy chain and two species of light chains, Lf21 and Lf18. Myosin from slow muscle (opener) consisted of two species of heavy chains and three species of light chains, Ls31, Ls21 and Ls18. Closer myosin containing both fast and slow types of muscles contained Lf21, Lf18, Ls31, Ls21 and Ls18. The actin-Mg2+-activated, Ca2+-activ ated, and K+-EDTA-activated ATPase activities of the fast muscle type of myosins were much higher than those of the slow muscle type of myos in. The ATPase activities of closer myosin were in-between. The optima l KCl concentration of the K+-EDTA-activated ATPase activity of crayfi sh myosins was around 0.4 M as compared to 1 M in rabbit skeletal musc le. Opener myosin was contaminated with a 130 kDa protein. The latter turned out to be a paramyosin isoform. Slow type of muscle including c loser muscle contained both 130 kDa and 105 kDa paramyosin isoforms. O n the other hand, fast muscle expressed 110 kDa paramyosin isoform.