alphas2caseïne

Alphas2-caseïne, also written αs2-casein, is a phosphoprotein and one of the four major caseins found in milk. It is encoded by the CSN1S2 gene and produced by mammary gland cells in many dairy mammals. Working together with αs1-, β- and κ-casein, αs2-casein is a constituent of the casein micelle, a colloidal particle that carries calcium and phosphate and helps stabilize milk against unwanted coagulation.

Form and function: αs2-casein is highly phosphorylated, with several serine residues that bind calcium. This property supports the formation and structure of casein micelles, in which αs2-casein interacts with other caseins and calcium phosphate nanoclusters. The protein contributes to milk's nutritional value and to its physicochemical behavior during processing, such as gelation in cheese making.

Genetics and variation: The CSN1S2 gene displays polymorphism, producing multiple αs2-casein isoforms. Expression and relative abundance vary by species, breed and individual. These genetic differences can influence milk composition, coagulation properties and cheese yield.

Role in dairy and nutrition: As a major dietary protein, αs2-casein provides amino acids upon digestion and participates in micelle structure that affects milk viscosity and processing characteristics. Caseins, including αs2, are also among common milk allergens; the role of αs2-casein in allergy varies between individuals.

Species distribution and research: αs2-casein occurs in the milks of many mammals but is not uniform across species. It is a subject of dairy genetics and proteomics, with ongoing research into its functions, variations and implications for dairy production.