Reduced receptor binding by a human interferon-gamma fragment lacking 11 carboxyl-terminal amino acids.
Treatment of recombinant human interferon-gamma (IFN-gamma) with either 1) the arginine-specific proteases clostripain or submaxillaris protease or 2) the broadly specific enzyme pronase produced a stable fragment with m.w. of 15,500. Structural analysis showed that the cleavage occurred between residues 129 and 130 and thus produced a fragment lacking only 11 carboxyl-terminal amino acids. The fragmented and untreated molecules showed identical amino-terminal amino acid sequences and were equally reactive with either polyclonal or monoclonal anti-IFN-gamma. IFN-gamma lacking carboxyl-terminal amino acids displayed a 1000- to 2000-fold reduction in its capacity to bind to cellular IFN-gamma receptors at 4 degrees C. Functionally the fragment showed a 50-fold reduction in its ability to induce antiviral activity in fibroblasts and a 10-fold reduction in its ability to induce Fc receptors on the human histiocytic lymphoma cell line U937. These results thus suggest that the carboxyl terminus of human IFN-gamma contributes significantly to the formation of the receptor-binding site of the molecule.
D000911:Antibodies, Monoclonal / Q000276:immunology; D002460:Cell Line; D005347:Fibroblasts; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism*; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism*; D010447:Peptide Hydrolases; D011485:Protein Binding; D011971:Receptors, Immunologic / Q000378:metabolism*; D017471:Receptors, Interferon; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D010446:Peptide Fragments; D011971:Receptors, Immunologic; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D007371:Interferon-gamma; D010447:Peptide Hydrolases