Relative Roles of the Head and Tail Portions of the Molecule in Heat‐Induced Gelation of Myosin

ABSTRACT Myosin molecules are cleaved by chymotrypsin digestion into two fragments: subfragment 1, which originates from the globular heads of myosin, and the myosin rod, which originates from the helical tail of the myosin molecule. The heat‐induced gelation of these subfragments was compared to that of intact myosin by measuring rigidity, turbidity, and other physico‐chemical characteristics of each system. Two features of the heat‐induced gelation of myosin, aggregation and three‐dimensional network formation were found to be imparted by the subfragment 1 and the rod, respectively. The former involves disulfide exchange and the latter relates to conformational changes arising from a partially irreversible helix‐coil transition during heating. Possible relationships are suggested between these physicochemical changes of the myosin head and tail regions upon heating and the heat‐induced gelation of myosin.