Ca2+-Induced Conformational Changes of Myosin from Silver Carp (Hypophthalmichthys molitrix) in Gelation

The role of Ca 2+ in gelation of myosin extracted from silver carp ( Hypophthalmichthys molitrix ) was investigated. Compared with the control, myosin with CaCl 2 showed higher turbidity and larger particle size, indicating that CaCl 2 contributed to myosin aggregation. Addition of CaCl 2 decreased the myosin thermostability and promoted the unfolding of myosin α-helical structure during heating. Moreover, CaCl 2 could increase surface hydrophobicity at low temperatures (20–40 °C) and promoted hydrophobic interactions. Meanwhile, it decreased the temperature of disulfide bond formation by about 10 °C. Addition of 10–40 mM CaCl 2 favored activation of the Ca 2+ -ATPase activity at 20 to 30 °C, but not obvious with elevated temperatures. Ca 2+ -ATPase activity of myosin was undetectable when heated above 60 °C because of severe structural damage of myosin heads. G’ at both the first and second peaks increased with increasing CaCl 2 concentration. Therefore, CaCl 2 was beneficial for gelation of myosin by inducing the unfolding of myosin and enhancing disulfide bonds along with hydrophobic interactions between neighboring myosin molecules.