Ca2+ -Induced Conformational Changes of Myosin from Silver Carp (Hypophthalmichthys molitrix ) in Gelation
Liwei Cao, Sisi Su, Joe M. Regenstein, Shanbai Xiong, Ru Liu
The role of Ca2+ in gelation of myosin extracted from silver carp (Hypophthalmichthys molitrix) was investigated. Compared with the control, myosin with CaCl2 showed higher turbidity and larger particle size, indicating that CaCl2 contributed to myosin aggregation. Addition of CaCl2 decreased the myosin thermostability and promoted the unfolding of myosin α-helical structure during heating. Moreover, CaCl2 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 CaCl2 favored activation of the Ca2+-ATPase activity at 20 to 30 °C, but not obvious with elevated temperatures. Ca2+-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 CaCl2 concentration. Therefore, CaCl2 was beneficial for gelation of myosin by inducing the unfolding of myosin and enhancing disulfide bonds along with hydrophobic interactions between neighboring myosin molecules.
Circular dichroism, Protein denaturation, Secondary structure, Biochemistry, Protein folding, Food science