Extraction and Functional Reformation of Thick Filaments in Chemically Skinned Molluscan Catch Muscle Fibers

Abstract

A method for the almost complete extraction of myosin from smooth muscle fibers of the anterior byssal retractor muscle (ABRM) of Mytilus edulis was developed, and functional reformation of thick filaments in the fibers was achieved. Complete removal of myosin from the glycerol-extracted ABRM fibers with a solution containing 600mM KCl, 5mM MgCl₂, and 5mM ATP was difficult. However, successive treatments of the ABRM fibers with glycerol and saponin made the plasma membrane permeable to Mg•ATP and myosin. The extraction of myosin completely eliminated the tension induced by the addition of Mg•ATP. Partial recovery of tension development was observed by irrigation of myosin into fibers from which myosin had been extracted. Similar results were obtained using rabbit myosin instead of ABRM myosin. Addition of heavy meromyosin, on the other hand, had a suppressive effect on the tension development, as is the case in glycerinated rabbit psoas muscle fibers.