Hexameric structure and assembly of the interleukin-6/IL-6 alpha-receptor/gp130 complex
Martin J Boulanger1, Dar-chone Chow, Elena E Brevnova
1Department of Microbiology and Immunology and Department of Structural Biology, Stanford University School of Medicine, Fairchild D319, 299 Campus Drive, Stanford, CA 94305-5124, USA.
Abstract:
Interleukin-6 (IL-6) is an immunoregulatory cytokine that activates a cell-surface signaling assembly composed of IL-6, the IL-6 alpha-receptor (IL-6Ralpha), 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-6Ralpha and then presented to gp130in 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.
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