キモトリプシン消化性からみたコイミオシンの構造特性

抄録

The chymotryptic digestibility of carp myosin in a filamentous form was compared with that of rabbit myosin. In the presence of EDTA, α-chymotrypsin cleaves head-tail junction selectively producing myosin subfragment-1 (S-1) and rod. Ca²⁺ addition protected this region from cleavage with rabbit myosin, and a small amount of heavy meromyosin (HMM) was produced. However, with carp myosin, the digestion under the same condition produced not only HMM but also roughly the same amount of S-1. This suggests the weak protection of the head-tail junction by Ca-binding light chain. S-1 production in the presence of Ca²⁺ was observed under all the conditions we tested; pH 6.3-8.3, 0.05-0.3_M KCl, and 10-20°C.
S-1 obtained by digesting in the presence of Ca²⁺ is indistinguishable from that obtained in EDTA medium not only in its subunit composition, but also in its biochemical properties (ATPase activity, actin binding, and thermal inactivation rate).