title: Localization of a receptor binding site on the IL-2 molecule.
abstract: The present study was performed to localize in the IL-2 molecule the active site responsible for interaction with the IL-2 receptor. To predict the receptor binding site on the IL-2 molecule, a computer programme based on the hypothesis that the active site will contain parts of the protein molecule having a high tendency to form a bend was utilized. The tendency to form a bend was evaluated by assessing the probability of beta-turn occurrence; the highest probability was found in the tetrapeptide Asn-Pro-Lys-Leu, occupying the positions 33-36 of the IL-2 molecule. Accordingly, the hexadecapeptide H-Cys-Nle-Gly-Ile-Asn-Asn-Tyr-Lys-Asn-Pro-Lys-Leu-Thr-Arg-Met-Leu-NH2 that spans over the predicted tetrapeptide Asn-Pro-Lys-Leu and comprises the region 27-40 from the IL-2 amino acid sequence was synthesized. This synthetic (I-16) peptide was found to selectively inhibit the IL-2-dependent uptake of 3H-TDR by CTLL cells, apparently by competing with IL-2 for the IL-2 receptor. The synthetic I-16 hexadecapeptide was conjugated to carrier (BSA) protein and used for immunization of rabbits. Resulting I-16 antibodies were capable of binding specifically to the I-16 hexadecapeptide in indirect ELISA test; they reacted substantially with IL-2-producing but not with IL-2-non-producing Jurkat cells in indirect cell membrane immunofluorescence, and inhibited activation of killer spleen cells with human recombinant IL-2 as detected by 51Cr microcytotoxicity assay. Taken together, these results suggest that at least one of the receptor contact sites of the IL-2 is localized within the N-terminal part of the molecule in the region defined by amino acids 27-40 and coded for by the exon 1 and 2.
mesh_terms: D000906:Antibodies; D001665:Binding Sites; D001681:Biological Assay; D003602:Cytotoxicity, Immunologic; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D005455:Fluorescent Antibody Technique; D007111:Immunity, Cellular; D007158:Immunologic Techniques; D007376:Interleukin-2 / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation; D009842:Oligopeptides / Q000138:chemical synthesis / Q000276:immunology / Q000378:metabolism; D011971:Receptors, Immunologic / Q000378:metabolism*; D015375:Receptors, Interleukin-2
chemical_list: D000906:Antibodies; D000939:Epitopes; D007376:Interleukin-2; D009842:Oligopeptides; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2