Alterations of the amino terminus of murine interferon-gamma: expression and biological activity.

To examine the relationship of murine interferon-gamma (MuIFN-gamma) protein structure to its biological function, several analogs (amino-terminal deletions) of MuIFN-gamma (type II IFN) have been constructed using synthetic oligonucleotide-directed primer repair. High-level expression was achieved through evaluation of such parameters as plasmid origin of replication, antibiotic resistance markers, and host background. The antiviral activity of these analogs varied depending upon the number of amino acids deleted. When the first nine amino acids of IFN-gamma were eliminated (10-136 analog), the protein product lacked detectable antiviral activity. The 10-136 analog but not the 12-136 analog was detectable by Western blots or Coomassie staining of protein gels. These results present the high-level (optimized) expression of several analogs of MuIFN-gamma and further define the role of the amino terminus of the protein with respect to antiviral activity.