Structure of hu.-rec. IFN gamma

Hu-IFN-gamma (143aa) was shortened by recombinant methods at the NH2-terminus by 1, 3 and 8 and at the COOH-end by 10, 11, 14 and 19aa. These mutants were expressed in bacterial cells, purified to more than 90 per cent and analysed in respect to molecular structure: dimer versus monomer and to antiviral activity. Loss of aa at the NH2-terminus conserves the dimeric structure whereas a shortage of 14 or 19 aa at the COOH-end results in a monomeric organisation. In contrast to all other mutants the two latter ones do not precipitate at high expression rates. Mutants shortened at the COOH-end by up to 11 aa even increase antiviral activity; a further additional take off by 3 or more aa drastically reduces activity. At the NH2-terminus the first 3 aa are not important for activity; a further shortage affects activity as well as a non precipitating monoclonal antibody, which recognizes the first 6 aa does neutralize antiviral activity. Mutants lacking 3 aa at the NH2-terminus or 11 at the C OOH-end, which both alone are fully active, show, combined in a double mutant, a 30 fold decrease in activity; this double mutant indicate and interaction of the ends of the protein for activity which may be important too for the structure.