Abstract: The present invention relates to an expression system comprising a DNA sequence encoding a polypeptide which ha a biological activity of human &kgr;-casein, the system comprising a 5′-flanking sequence capable of mediating expression of said DNA sequence. In preferred embodiments the 5′-flanking sequence is from a milk protein gene of a mammal such as a casein gene or whey acidic protein (WAP) gene and the DNA sequence contains at least one intron sequence. The invention further relates to DNA sequences, replicable expression vectors and cells harboring said vectors, recombinant polypeptide e.g. in glycosylated form, and milk, infant formula or nutrient supplement comprising recombinant polypeptide.

Abstract: The present invention relates to a DNA sequence encoding the human milk protein .beta.-casein or an analogue or variant thereof which has either the calcium binding activity of human .beta.-casein, or opioid activity, or angiotensin converting enzyme (ACE) inhibitory activity, or a combination of any two or three of these activities. The DNA sequence may optionally contain one or more intron sequences and permissive RNA splice signals. The DNA sequence is used in the production of recombinant human .beta.-casein, advantageously by means of production in transgenic non-human mammals such as bovine species. In one embodiment, the DNA sequence is inserted into a milk protein gene of a mammal such as a whey acidic protein (WAP) gene. The main use of the recombinant human .beta.-casein is as a constituent of infant formulae. It is contemplated that the recombinant human .beta.