MYOSIN FROM STRIATED ADDUCTOR MUSCLE OF CHLAMYS-NIPPONENSIS-AKAZARA

Myosin was isolated from striated adductor muscle of Akazara shellfish, C. nipponensis-akazara, and purified on DEAE-Sephadex A50. The sedimentation constant .**GRAPHIC**. and the intrinsic viscosity, [.eta.] of purified Akazara myosin were estimated to be 6.6 S and 2.10 dl/g, respectively. Akazara myosin was similar to scallop myosin. Only 1 size of light-chain component (17,000 daltons) was detectable in SDS[sodium dodecyl sulfate]-gel electrophoresis of Akazara myosin, but 2 types of light-chain component were seen in urea gel electrophoresis; these were equivalent to EDTA-light chain and SH-light chain of scallop myosin. The molar ratio of heavy chain (206,000 daltons), EDTA-light chain and SH-light chain in Akazara myosin was estimated, from the staining densities of gel electrophoretic bands, to be approximately 1:1:1. The EDTA-washing procedure removed EDTA-light chain only, causing desensitization of Akazara myosin. EDTA-light chain isolated from Akazara myofibrils resensitized EDTA-washed Akazara myosin. Akazara myosin was different from scallop myosin in 2 important properties. Complete removal of EDTA-light chains was required to achieve a complete loss of Ca sensitivity, and full resensitization was attained on recombination of EDTA-light chains with desensitized myosin prepared essentially free from EDTA-light chains. EDTA-light chains isolated from Akazara myofibrils show a Ca-induced UV absorption difference spectrum.