Proteolytic Digestion of Myosin from Abalone Haliotis discus Smooth Muscle.

Abstract

Abalone myosin was digested with proteases, (trypsin, chymotrypsin, nagarse, papain) in the presence of CaCl₂ or EDTA. The time course of the digestion and the properties of degradation products were investigated by SDS-polyacrylamide gel electrophoresis.
In the presence of CaCl₂, myosin light chains were not digested, but in the presence of EDTA, regulatory light chains disappeared at first, followed by SH light chains.
Heavy meromyosin (HMM) was obtained by tryptic and chymotryptic digestion of abalone myosin. These HMM had multiple cleavages in the heavy chain (HC) region.
Subfragment-1 (S1) was also obtained by chymotryptic, nagarse and papain digestion and by tryptic digestion in the presence of EDTA. The molecular weight of S1 HC was 90-100 kilodalton (kD). Papain S1 obtained in the presence of CaCl₂ had a single HC (94kD) and two light chains, but other S1 had intra-cleavages in the HC region.
These results indicate that abalone myosin has protesae sensitive region whose cleavage leads to HMM or S1, like skeletal muscle myosin, homogeneous S1 preparation is obtained by diges-tion with papain.