What kinds of proteins can be produced transgenically in milk?
Efficient methods now exist to produce a wide variety of biologically active recombinant proteins — both large and small, simple and complex. GTC Biotherapeutics, has successfully produced several different classes of proteins in the milk of transgenic animals. Some of these proteins are complex glycosylated proteins, which contain specific sugars attached at precise sites in the mature protein molecule. We have produced many monoclonal antibodies, which are made up of two pairs of different protein chains that must be assembled correctly in vivo. In addition, we have produced fusion proteins that combine the active sites from two different proteins into one molecule, such as a biologically active enzyme fused to targeting sequences from an anti-tumor antibody. It has been observed that these fusions proteins may be difficult to secrete from tissue culture cells. The mammary gland is capable of high level expression of these proteins. They are properly folded in that they have the cor
