Interaction Mechanism of Casein with Ferritin and Iron Ion: The Structure, Iron Oxidation/Release, and Functionality Exploration

Ferritin is a major iron storage protein, which can regulate the dynamic balance of iron in organisms. Casein, the major protein in milk, has a unique phosphorylated structure that makes it a natural and versatile metal chelator. This study investigated the interaction mechanism of casein with shrimp ferritin and iron ions and evaluated the structure, iron oxidation/release, and functionality of ferritin. The results indicated that Fe²⁺ can interact with ferritin and casein to form ferritin-casein-Fe complexes, which altered the protein conformation. The interaction between ferritin and casein is mainly driven by hydrophobic interaction, hydrogen bond, and electrostatic force. The addition of casein can inhibit the oxidation precipitation and reduction release of iron in ferritin. Moreover, the existence of casein further improved the functional properties of ferritin, including emulsification, foaming, and thermal stability. This finding offers a theoretical basis for the understanding of protein interactions and regulation of iron ions.