Characterization of a synthetic peptide corresponding to a receptor binding domain of mouse interferon .gamma

• Published in: Biochemistry (Easton) Vol. 30; no. 23; pp. 5784 - 5789
• Main Authors: Magazine, Harold I, Johnson, Howard M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 11.06.1991
• Subjects: 550201 - Biochemistry- Tracer Techniques; Amino Acid Sequence; Animals; ANTIBODIES; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; Binding, Competitive; Cattle; Circular Dichroism; DAYS LIVING RADIOISOTOPES; DICHROISM; ELECTRON CAPTURE RADIOISOTOPES; GLYCOPROTEINS; GROWTH FACTORS; Humans; INTERFERON; Interferon-gamma - chemistry; Interferon-gamma - metabolism; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; IODINE 125; IODINE ISOTOPES; ISOTOPES; LYMPHOKINES; MAGNETIC CIRCULAR DICHROISM; MEMBRANE PROTEINS; Mice; MITOGENS; Molecular Sequence Data; MONOCLONAL ANTIBODIES; NUCLEI; ODD-EVEN NUCLEI; ORGANIC COMPOUNDS; Peptide Fragments - chemistry; Peptide Fragments - metabolism; PEPTIDES; Protein Conformation; PROTEINS; RADIOISOTOPES; Rats; RECEPTORS; Receptors, Immunologic - chemistry; Receptors, Immunologic - metabolism; Receptors, Interferon; SPECTRA; Structure-Activity Relationship; ULTRAVIOLET SPECTRA
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00237a022

A receptor binding region of mouse interferon gamma (IFN gamma) has previously been localized to the N-terminal 39 amino acids of the molecule by use of synthetic peptides and monoclonal antibodies. In this report, a detailed analysis of the synthetic peptide corresponding to this region, IFN gamma (1-39), is presented. Circular dichroism (CD) spectroscopy indicated that the peptide has stable secondary structure under aqueous conditions and adopts a combination of alpha-helical and random structure. A peptide lacking two N-terminal amino acids, IFN gamma (3-39), had similar secondary structure and equivalent ability to compete for receptor binding, while peptides lacking four or more N-terminal residues had reduced alpha-helical structure and did not inhibit 125I-IFN gamma binding. Substitution of proline, a helix-destabilizing amino acid, for leucine (residue 8) of a predicted amphipathic alpha-helix (residues 3-12), IFN gamma (1-39) [Pro]8, resulted in a substantial reduction in the helical content of the peptide, supporting the presence of helical structure in this region. However, destabilization of the helix did not reduce the competitive ability of the peptide. A peptide lacking eight C-terminal residues, IFN gamma (1-31), did not block 125I-IFN gamma binding and had no detectable alpha-helical structure, suggesting a requirement of the predicted second alpha-helix (residues 20-34) for receptor interaction and helix stabilization. Substitution of phenylalanine for tyrosine at position 14, IFN gamma (1-39) [Phe]14, a central location of a predicted omega-loop structure, did not affect the secondary structure associated with the region yet resulted in a 30-fold increase in receptor competition.