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Intedeukin-2 (IL-2) is an immunoregulatory cytokine that binds sequentially to the alpha (IL-2Rα), beta (IL-2Rβ), and common gamma chain ([γ.sub.c]) receptor subunits. Here we present the 2.8 angstrom crystal structure of a complex between human IL-2 and IL-2Rα, which interact in a docking mode distinct from that of other cytokine receptor complexes. IL-2Rα is composed of strandswapped 'sushi-like' domains, unlike the classical cytokine receptor fold. As a result of this domain swap, IL-2Rα uses a composite surface to dock into a groove on IL-2 that also serves as a binding site for antagonist drugs. With this complex, we now have representative structures for each class of hematopoietic cytokine receptor-docking modules., Interleukin-2 (IL-2), which is one of the first cytokines identified and a member of the four-helix bundle cytokine superfamily, acts at the heart of the immune response (1). IL-2 and [...]

Interleukin-6 (IL-6) is an immunoregulatory cytokine that activates a cell-surface signaling assembly composed of IL-6, the IL-6 α-receptor (IL-6Rα), and the shared signaling receptor gp130. The 3.65 angstrom-resolution structure of the extracellular signaling complex reveals a hexameric, interlocking assembly mediated by a total of 10 symmetry-related, thermodynamically coupled interfaces. Assembly of the hexameric complex occurs sequentially: IL-6 is first engaged by IL-6Rα and then presented to gp130 in the proper geometry to facilitate a cooperative transition into the high-affinity, signaling-competent hexamer. The quaternary structures of other IL-6/IL-12 family signaling complexes are likely constructed by means of a similar topological blueprint., Gp130 is a shared signal-transducing receptor for a family of more than 10 different four-helix-bundle cytokines, including IL-6, leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF), oncostatin-M (OSM), and others [...]

Interleukin-6 (IL-6) is an immunoregulatory cytokine that activates a cell-surface signaling assembly composed of IL-6, the IL-6 a-receptor (IL-6Ra), and the shared signaling receptor gp130. The 3.65 angstrom-resolution structure of the extracellular signaling complex reveals a hexameric, interlocking assembly mediated by a total of 10 symmetry-related, thermodynamically coupled interfaces. Assembly of the hexameric complex occurs sequentially: IL-6 is first engaged by IL-6Ra and then presented to gp130 in the proper geometry to facilitate a cooperative transition into the high-affinity, signaling-competent hexamer. The quaternary structures of other IL-6/IL-12 family signaling complexes are likely constructed by means of a similar topological blueprint. [ABSTRACT FROM AUTHOR]