Two contiguous residues in human interleukin-3, Asp21 and Glu22, selectively interact with the α- and β-chains of its receptor and participate in function

S. C. Barry, C. J. Bagley, J. Phillips, M. Dottore, Bronwyn Cambareri, P. Moretti, R. D'Andrea, G. J. Goodall, M. F. Shannon, M. A. Vadas, A. F. Lopez

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We have previously reported that the predicted first helix of human interleukin (IL)-3 contains a hydrophilic region encompassing residues Asp21, Glu22, and Thr25 that is crucial for biological activity and IL- 3 receptor binding. Using single amino acid substitution mutagenesis, we have now determined that Asp21 and Glu22, but not Thr25, were crucial for full IL-3 activity. Mutant D21R was 30-fold less potent than wild type IL-3 in the stimulation of biological activity. It also exhibited a similar reduction in its ability to bind to the cloned high affinity IL-3 receptor complex (α- and β-chains) or to the receptor α-chain alone, indicating that residue 21 is involved in contacts with the α-chain. Mutant E22R was approximately 20,000-fold less potent than wild type IL-3 in the stimulation of biological activity and in binding to the IL-3 receptor high affinity complex. However, the binding of E22R to the IL-3 receptor α-chain alone was similar to that of wild type IL-3, suggesting that this mutant was defective in interactions with the receptor β-chain. These results show that two contiguous residues in the N-terminal region of IL-3 mediate binding to the two different chains of the IL-3 receptor and emphasize the functional significance of the conserved Glu in the first helix of the IL-3, granulocyte-macrophage colony-stimulating factor, and IL-5 cytokine subfamily.

Original languageEnglish
Pages (from-to)8488-8492
Number of pages5
JournalJournal of Biological Chemistry
Issue number11
Publication statusPublished or Issued - 1994
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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