Structure and Activity of Glycosylated Human Interferon-γ

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Abstract
Structural properties and activity of recombinant human interferon-γ (IFN-γ) purified from Chinese hamster ovary (CHO) cells or a natural source were determined and compared with those of Escherichia coli-derived IFN-γ. One preparation of CHO-derived IFN-γ showed three bands, with the middle band being a doublet, in a SDS-polyacrylamide gel. The two higher-molecular-weight bands were shown to be glycosylated. Western blot analysis indicated that the three bands are IFN-γ and lack an intact carboxyl terminus. The circular dichroic (CD) spectra showed that conformation of the CHO-derived IFN-γ is similar in the native state, in acid, and after renaturation from acid to the E. coli-derived IFN-γ. These results indicate that neither glycosylation nor carboxy-terminal processing affects conformational properties of the protein, as detected by CD spectroscopy. However, the antiviral activity was fourfold lower for the preparation of CHO-derived IFN-γ than for the E. coli-derived IFN-γ. A different preparation or a natural IFN-γ preparation with less extensive carboxy-terminal processing showed similar conformational properties and antiviral activity to the E. coli-derived IFN-γ. These results indicate that the carboxyl terminus, but not glycosylation, plays an important role in the antiviral activity of IFN-γ.