CSN2 encodes beta-casein, a major milk protein with pleiotropic functions across multiple biological contexts. In lactation, beta-casein plays a critical structural role in determining casein micelle surface properties [UniProt]. The protein exhibits cysteine-type endopeptidase inhibitor activity and calcium ion binding capacity [GO Annotations], contributing to milk protein organization and mineral transport. Beyond lactation, CSN2 functions in post-translational modification cascades. CSN2 phosphorylation by CK2 is required for deneddylase CSN to sequester CRL4, a Cullin RING ligase complex. In glucose-stimulated conditions, O-GlcNAcylation of CK2 impedes CSN2 phosphorylation, promoting CRL4COP1 assembly and p53 degradation, thereby derepressing glycolytic enzymes and supporting cancer cell proliferation 1. This glucose-induced signaling axis links hyperglycemia to mutation-independent p53 checkpoint bypass. Genetically, CSN2 exhibits two major bovine variants (A1 and A2) with population health implications. The A1 variant produces Beta-Casomorphin-7, a bioactive opioid potentially associated with coronary heart disease, type 1 diabetes, and neurological disorders 23. A2 variants lack this epitope. Breed-specific allele frequencies vary geographically, with implications for selective breeding programs targeting improved milk safety 34. CSN2 is localized to chromosome 4-q21 5.