Effect of amino-terminal processing by Staphylococcus aureus V-8 protease on activity and structure of recombinant human interferon-gamma.

Treatment of recombinant human interferon-gamma (rHuIFN-gamma) with Staphylococcus aureus V-8 protease generated a transiently stable species that lacks 10 amino-terminal residues. This protein showed distinct secondary and higher-order structures with an alpha-helical content of 31%, suggesting that the secondary and tertiary structure largely remain upon removal of 10 amino-terminal residues. The antiviral activity was abolished, or greatly reduced, for this species relative to the intact protein. These results suggest an important role for the amino-terminal portion in the activity of human interferon-gamma. Since the digested protein is difficult to refold from the acid-denatured state, it was concluded that, although not essential for maintaining the core structure of the protein, the amino-terminal portion is critical for refolding the protein from acid.