1 H, 13 C and 15 N resonance assignments of a highly-soluble murine interleukin-3 analogue with wild-type bioactivity

Interleukin-3 (IL-3) is a cytokine that acts as a critical mediator of inflammation and immune responses to infections. IL-3, like interleukin-5 (IL-5) and granulocyte-macrophage colony stimulating factor (GM-CSF), exerts its effects on target cells via receptors composed of cytokine-specific α-subunits and a common β-subunit (βc-subunit, shared with IL-5 and GM-CSF). In contrast to humans, mice also possess an additional β-receptor, β IL-3 , that can specifically bind IL-3. Except for a study carried out on an analogue of human IL-3 that contains 14 mutations, structure-related studies of IL-3 have been very limited, largely because of its poor solution behaviour. Here we report 1 H, 13 C, and 15 N chemical shift assignments of murine IL-3 comprising residues 33–156 (SWISS-PROT accession number: P01586), in which the only mutation is an alanine substitution of Cys105. The mIL-3 construct used in the present study was engineered by eliminating residues 27–32 of the N-terminus (the first 26 residues of the primary sequence of mIL-3 are cleaved in vivo during secretion), the C-terminal 10 residues (157–166), and a disulfide bond between Cys105 and Cys166 that is poorly conserved in orthologue sequences. The new construct vastly improves the solubility of murine IL-3 while maintaining its wild-type biological activity.