Structural characterization of recombinant human interferon-gammas derived from two different mammalian cells

Recombinant human interferon-gammas (rHuIFN-gamma s) were obtained from two different mammalian cells (mouse C127 cells and Chinese hamster ovary, CHO, cells) cultured in a microcarrier culture system. Both rHuIFN-gamma s were purified using sequential chromatographies for their comparison of structural properties. The peptide maps of HuIFN-gamma s digested with V8 protease and Western blot analysis demonstrated that C127 cells yielded mainly about 25kDa component and CHO cells produced about 25kDa and about 20kDa components. By the identification of glycosylated peptides, it was suggested that 20kDa and 25kDa components are glycosylated at one and at two sites, respectively. C-terminal amino acid sequence analysis indicated that both rHuIFN-gamma s consisted of at least six different species lacking 2 to 16 amino acid residues from C-terminus, so that C-termini of both rHuIFN-gamma s were slightly different from each other. Amino acid sequence and composition analyses of N-terminal peptides demonstrated that N-termini of both rHuIFN-gamma s were blocked and were supposed to be identical with that of natural HuIFN-gamma. These results suggested that different molecular heterogeneities of rHuIFN-gamma s resulted from the difference of post-translational modifications of host cells.