The N-terminus and C-terminus of IFN-gamma are binding domains for cloned soluble IFN-gamma receptor

• Published in: The Journal of immunology (1950) Vol. 149; no. 2; pp. 517 - 520
• Main Authors: Griggs, ND, Jarpe, MA, Pace, JL, Russell, SW, Johnson, HM
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Assoc Immnol 15.07.1992; American Association of Immunologists
• Subjects: Amino Acid Sequence; Analysis of the immune response. Humoral and cellular immunity; Animals; Biological and medical sciences; Cloning, Molecular; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Immunobiology; Interferon-gamma - metabolism; Lymphokines, interleukins ( function, expression); Mice; Molecular Sequence Data; Peptide Fragments - metabolism; Receptors, Immunologic - metabolism; Receptors, Interferon; Regulatory factors and their cellular receptors; Solubility; C terminal-Sequence; Vertebrata; Mammalia; Synthetic product; Mouse; Rodentia; N terminal-Sequence; Molecular interaction; Binding site; Soluble form; Gamma interferon; Biological receptor
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.149.2.517

The mechanism of binding of murine IFN-gamma to its receptor has not been determined. We have studied this mechanism by examining the binding of overlapping synthetic peptides of IFN-gamma to cloned soluble murine IFN-gamma R. IFN-gamma (1-39) and IFN-gamma (95-133) were able to compete with [125I]IFN-gamma for binding to cloned soluble receptor. Peptides corresponding to the inner region of IFN-gamma--IFN-gamma (36-60), IFN-gamma (54-91), and IFN-gamma (78-107)--showed a markedly reduced ability to compete with [125I]IFN-gamma for receptor binding relative to the N-terminal and C-terminal peptides. In direct binding studies, the binding of [125I]-IFN-gamma (1-39) to soluble receptor could only be competed by IFN-gamma (1-39) and IFN-gamma and not by any of the other peptides including IFN-gamma (95-133). This suggests that the N- and C-termini of IFN-gamma bind to different regions of the receptor. These data in conjunction with previous structure/function studies and x-ray crystallographic data have allowed us to formulate a "velcro-key" model of IFN-gamma binding to receptor that involves both the N- and C-terminal domains. The N-terminus binds in the classical "lock-and-key" manner characterized by specific ligand-receptor binding. The hydrophilic C-terminus binds to a region of the receptor distinct from the N-terminus likely through the polycationic region, which is conserved across species barriers. Binding of this type would exhibit high affinity and low specificity similar to a piece of velcro. This interaction becomes specific when the C-terminus is in the context of the whole IFN-gamma molecule and may act to increase the affinity of receptor binding and/or facilitate signal transduction.