Investigations of Soybean 11S Protein and Myosin Interaction by Solubility, Turbidity and Titration Studies

Solubility tests, turbidity tests, and titration experiments were employed to study the possible protein‐protein interactions between purified soybean 11S protein and skeletal muscle myosin and the involvement of protein subunits in the interactions. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) was used as an analytical tool for identification of the protein species. These tests indicate that these proteins interacted at temperatures between 85°C and 100°C. Solubility and titration experiments showed that acidic subunits of soybean US protein had little or no interaction with myosin heavy chain subunits. In contrast, soybean 11S basic subunits interacted with myosin heavy chains. The SDS‐PAGE method indicated that eight commercial soy protein isolates had a similar protein species composition, but certain proteins in some isolates had lost their availability for water extraction. This may account for different functional properties exhibited by differen soy protein isolates.