Effect of L-lysine and L-arginine on Solubility and Conformation of Tilapia Myosin at Three Ionic Strengths
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Abstract:
Myosin was extracted from tilapia (Oreochromis niloticus) muscle, and 5.0 mg/mL myosin was dialyzed against three ionic strengths of a solution containing 10 mmol/L L-lysine and L-arginine. Effect of amino acid on solubilization of myosin was investigated at different ionic strengths. The solubility of myosin increased with increasing ionic strength (p<0.05). In a high-ionic-strength (600 mmol/L KCl) solution, little effect of L-lysine and L-arginine was detected on solubility, turbidity, and secondary structure on tilapia myosin. In a low-ionic-strength (1 mmol/L KCl) solution, the presence of L-lysine and L-arginine inhibited formation of myosin filament, and caused a decrease in turbidity, significantly increased solubility, accompanied by a significant increase in α-helix content of solubilized myosin. Nevertheless, in a physiological-ionic-strength (0.15 mol/L KCl) solution, a decrease in turbidity and increase in solubility of tilapia myosin was detected, accompanied by a significant increase in surface hydrophobicity (p<0.05) and loss of α-helix content. The myosin filament was completely depolymerized, and the protein system was more dispersed at physiological ionic strength with L-lysine and L-arginine. The results indicated that L-lysine and L-arginine changed the pH of myosin solution because of a specific role in disrupting electrostatic interactions, which resulted in the solubilization of myosin at low ionic strength.
