Crystal structure of human recombinant interleukin‐4 at 2.25 Å resolution

Authors:
  • AWAlexander Wlodaver
    Alexander Wlodaver
  • APAlexander Pavlovsky
    Alexander Pavlovsky
  • AGAlla Gustchina
    Alla Gustchina

Abstract
The crystal structure of human recombinant interleukin‐4 (IL‐4) has been solved by multiple isomorphous replacement, and refined to an R factor of 0.218 at 2.25 Å resolution. The molecule is a left‐handed four‐helix bundle with a short stretch of β sheet. The structure bears close resemblance to other cytokines such as granulocyte‐macrophage colony stimulating factor (GM‐CSF). Although no sequence similarity of IL‐4 to GM‐CSF and other related cytokines has been previously postulated, structure‐based alignment of IL‐4 and GM‐CSF revealed that the core of the molecules, including large parts of all four helices and extending over half of the molecule, has 30% sequence identity. This may have identified regions which are not only important to maintain structure, but could also play a role in receptor binding.

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