Interferon-gamma is a homodimeric protein with 143 amino acids. It is glycosylated on two asparagins. Its three-dimensional structure is meanwhile published. Interferon-gamma is less antiviral than the type I Interferons, but has much higher antiproliferative and immunomodulatory activities. It is synthesized in bacterial cells. Although they are not able to synthesize the glycosylation it seems to have no effect for the activities. Unglycosylated Interferon-gamma is a highly basic protein with an IP of about 10. In comparison to the type 1 interferons it is less pH-stable and with a Tm of 52°C shows a much lower thermostability.
For the reasons stated above several groups (including ours) have tried to generate a more stable or more active interferon through a modification of its DNA-code. Through shortening the C-terminus, a second generation Interferon-gamma was generated This new Interferon-gamma IFN-gamma-HA (high activity) is patented and now offered for further clinical development.
In the next step by rational protein design a third generation Interferon-gamma was generated. The specific incorporation of a disulfide bridge into the Interferon-gamma molecule resulted in a tightly packed IFN-gamma-HS (high stability) which shows an increased melting point of 70°C. This new Interferon-gamma is thouroughly characterized, patented, and now offered for further clinical development.