The role of the extension region on the structural and physicochemical characteristics of the α‐subunit of β‐conglycinin: implications of pH value and ionic strength

BACKGROUND To clarify the role of the extension region on the structure–functional relationship of the α‐subunit of β‐conglycinin, α‐subunit and its segment of the core region (αc‐subunit) were expressed via an Escherichia coli system. Their physicochemical properties were compared under acid, neutral or alkaline conditions (pH 4.0, 7.0, and 8.0) and high or low ionic strength (μ = 0.05 and 0.5), respectively. RESULTS The results showed that the extension region contributed to increasing thermal stability, especially at low ionic strength under acidic and neutral conditions. The extension region stabilized the α‐subunit with high solubility, low turbidity, and small particle size under neutral and alkaline conditions, whereas these impacts were suppressed at a high ionic strength and acidic conditions. Surface hydrophobicity of the α‐subunit decreased under acidic and alkaline conditions without being interfered with by ionic strength. CONCLUSION It can be concluded that the extension region played different roles under different pH and ionic strength conditions. These factors should be specified carefully and speculated individually to explore the more detailed and profound nature of β‐conglycinin at the submolecular level. The results could benefit a better understanding of the relationship between domain structure and functions of soybean protein. © 2022 Society of Chemical Industry.