CARP NATURAL ACTOMYOSIN - THERMAL-DENATURATION MECHANISM

Structural changes of actomyosin, the major protein of muscle, on heating have been estimated on ATPase activity. We investigated carp actomyosin molecule changes on heating based on biophysical and biochemical techniques. Actomyosin molecules began to unfold at approximate to 30 degrees C. Hydrophobic amino acid residues and SH groups, which had been inside the molecule, emerged to the surface. Because of hydrophobic interactions and disulfide bonds, actomyosin molecules formed aggregates. At > 40 degrees C, a part of myosin molecules was dissociated from actin filaments. Thus, dissociated myosin and the myosin-lacking molecules co-existed. In addition, fragmentation of actin filaments was observed, which was associated with the dissociation of myosin molecules. At greater than or equal to 60 degrees C actomyosin molecules formed larger aggregates, in which no filamentous shape was observed. This aggregation occurred mainly by formation of SS bonds.