Structure of an epitope in an immunodominant region of the interferon-gamma molecule that is involved in receptor interaction.
An amino-terminal immunodominant region of murine interferon-gamma (IFN-gamma) that may be involved in function is characterized using a neutralizing amino-terminal-specific monoclonal antibody (mAb) and synthetic peptides. Competition studies with peptide truncations determined that residues 3, 4, and 5 of IFN-gamma were required for binding to the mAb. These residues are predicted to participate in an amphipathic alpha-helix spanning residues 3-11 of IFN-gamma. Conservative peptide analogs that maintain the amphipathicity of the alpha-helix of IFN-gamma (1-20) retained the ability to block IFN-gamma binding to mAb. Peptide analogs with substitutions that disrupted the amphipathicity of the alpha-helix lost their ability to block binding. The tyrosine at position 14 was required as its removal in carboxy-terminal truncations caused the loss of blocking ability. We conclude that the IFN-gamma epitope for the neutralizing mAb involves residues 3-14, spanning 12 residues, and it appears that residues 3, 4, 5, and 14 are an important part of the epitope. Based on these characteristics and the observation that most continuous epitopes are reported to involve shorter regions of up to 8 residues, this epitope may be described as a linear discontinuous epitope that may require the amphipathic helix. The data presented here provide further insight to the structure of a site that is involved in receptor interaction.
Department of Microbiology and Cell Science, University of Florida, Gainesville 32611.
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Johnson
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D002942:Circular Dichroism; D006224:Cricetinae; D000939:Epitopes / Q000032:analysis*; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology; D011487:Protein Conformation; D011863:Radioimmunoassay; D011971:Receptors, Immunologic / Q000378:metabolism*; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship
D000911:Antibodies, Monoclonal; D000939:Epitopes; D010446:Peptide Fragments; D011971:Receptors, Immunologic; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D007371:Interferon-gamma