Expression and Characterization of Bioactive Recombinant Human α-Lactalbumin in the Milk of Transgenic Cloned Cows

Improvement of the nutritional value of cow milk with transgenic expression of recombinant human α-lactalbumin (α-LA) has been previously attempted. However, the detailed characterization of the recombinant protein and analysis of the transgenic milk components are not explored yet. Here, we first report production of healthy transgenic cows by somatic cell nuclear transfer, in which expression of up to 1.55 g/L of recombinant human α-LA was achieved. The recombinant human α-LA was purified from transgenic milk and displayed physicochemical properties similar to its natural counterpart with respect to molecular weight, structure, and regulatory activity for β-1,4-galactosyltransferase. Additionally, no N-glycosylation was found in the recombinant human α-LA, whereas the endogenous bovine α-LA was glycosylated at the unusual site 71Asn-Ile-73Cys. Compared with milk from nontransgenic cows, expression of the transgene did not materially alter milk composition, such as fat and protein content. Our research thus provides scientific evidence supporting the feasibility of humanizing cow milk.