Human interferon-gamma lacking 23 COOH-terminal amino acids is biologically active

We constructed five mutated cDNAs encoding human interferon-gamma (IFN-gamma) derivatives lacking 19-23 COOH-terminal residues and expressed them in Escherichia coli. All the derivatives were purified to homogeneity. They showed substantially the same order of antiviral activity in vitro as the intact molecule, and behaved as a dimer. The far- and near-UV circular dichroism spectra of the derivatives were quite similar to those of the intact one. These results indicate that the 23 COOH-terminal amino acids at least are not essential for achieving the full antiviral activity and constructing the higher structure of human IFN-gamma.