INTERFERON-GAMMA RECEPTOR EXTRACELLULAR DOMAIN-IGG FUSION PROTEIN PRODUCED IN CHINESE-HAMSTER OVARY CELLS AS MIXTURE OF GLYCOFORMS

Glycosylation of proteins fulfills important functions and because of its diversity contributes to apparent protein heterogeneity, We invest igated the heterogeneity of a fusion protein comprising the extracellu lar domain of the human interferon-gamma (IFN-gamma) receptor and part s of the human IgG(3) constant region, a potential IFN-gamma antagonis t, The protein was produced in Chinese hamster ovary (CHO) cells and w as secreted into the culture medium as an 175 kD glycoprotein. Glycosy lation represented approximately one-third of the apparent molecular m ass of the fusion protein, consisted of N- and O-linked carbohydrate m oieties, and included sialic acid residues as part of both N- and O-li nked oligosaccharides, Fusion protein forms with different apparent mo lecular masses and charges were separated by ion-exchange chromatograp hy. Preparative electrofocusing revealed a wide spectrum of glycoforms . Glycosylation of the fusion protein and of soluble IFN-gamma recepto rs, comprising the extracellular domain of the native sequence, expres sed in insect and CHO cells did not interfere with affinity of ligand binding.