Identification of the Discontinuous Binding Site in Human Interleukin 1β for the Type I Interleukin 1 Receptor

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 88; no. 24; pp. 11182 - 11186
• Main Authors: LABRIOLA-TOMPKINS, E, CHANDRAN, C, KAFFKA, K. L, BIODIN, D, GRAVES, B. J, HATADA, M, MADISON, V. S, KARAS, J, KILIAN, P. L, JU, G
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 15.12.1991; National Acad Sciences
• Subjects: Amino Acid Sequence; Amino acids; Analysis of the immune response. Humoral and cellular immunity; Binding Sites; Biological and medical sciences; CHO cells; Cloning, Molecular; Competitive binding; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Humans; Immunobiology; Inhibitory concentration 50; Interleukin-1 - chemistry; Interleukin-1 - genetics; Interleukin-1 - metabolism; Interleukins; Kinetics; Ligands; Mice; Models, Molecular; Mutagenesis; Mutagenesis, Site-Directed; Protein Conformation; Receptors; Receptors, Immunologic - metabolism; Receptors, Interleukin-1; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Regulatory factors and their cellular receptors; X-Ray Diffraction; Human; Molecular interaction; Identification; Binding site; Cytokine; Biological receptor
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.88.24.11182

Human interleukin 1β (IL-1β) exerts its diverse biological effects by binding to specific receptors on target cells. Two types of IL-1 receptor (IL-1R) have been identified: the type I IL-1R (p80) and the type II IL-1R (p68). Using site-specific mutagenesis, we have identified the binding site on IL-1β for the murine type I IL-1R. Analogs of the IL-1β protein containing defined amino acid substitutions were produced and tested for competitive binding to the two IL-1Rs. Substitutions of the amino acids at seven positions resulted in analogs that had ≥100-fold reductions in competitive binding to the type I IL-1R, while maintaining substantial binding to the type II IL-1R. These seven amino acids (Arg-4, Leu-6, Phe-46, Ile-56, Lys-93, Lys-103, and Glu-105) are clustered in the IL-1β molecule, forming a discontinuous binding site. The side chains of all seven residues are exposed on the surface of IL-1β. The cumulative binding energies contributed by each of the residues predict a binding affinity that is consistent with the observed Kdof the wild-type protein for the type I IL-1R.