Functional and dysfunctional folding, association and aggregation of caseins

Area of Science:

• Biochemistry
• Protein Science
• Food Science

Background:

• Caseins are intrinsically disordered proteins (IDPs) found in milk.
• They form complex, amorphous particles called casein micelles containing calcium phosphate nanoclusters.
• Casein micelles differ structurally from detergent micelles.

Purpose of the Study:

• To elucidate the structural properties and functional roles of caseins and casein micelles.
• To understand how caseins prevent amyloid formation and pathological calcification.
• To explain the mechanism of calcium phosphate sequestration by caseins.

Main Methods:

• Analysis of intrinsically disordered protein (IDP) properties.
• Investigation of protein-protein interactions and complex formation.
• Study of calcium phosphate binding and micelle stability.

Main Results:

• Caseins possess flexible conformations and poly-L-proline II structures, not hydrophobic characteristics.
• They form polydisperse, fuzzy complexes through polar and non-polar interactions.
• Caseins act as molecular chaperones, suppressing amyloid formation within their complexes.
• Multiply-phosphorylated sequences enable stable sequestration of calcium phosphate nanoclusters.
• Casein micelles provide a digestible source of calcium and phosphate for neonates.
• These structures protect the mammary gland from amyloidosis and pathological calcification.

Conclusions:

• Casein micelle structure is crucial for nutrient delivery and maternal health.
• The unique properties of caseins as IDPs are essential for their biological functions.
• Casein micelles represent a sophisticated biological system for mineral transport and protein stabilization.