Cloning and expression of an interleukin‐1β precursor and its conversion to interleukin‐1β

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Abstract
A gene coding for a N-terminal precursor of interleukin-1β (IL-1β) was cloned and expressed in E. coli. The isolated Met-Glu-Ala-Glu-IL-1β precursor was enzymatically converted to IL-1β by means of dipeptidylaminopeptidase (DAP I). This method ensured a correct N-terminal residue and the often observed expression of Met-IL-1β was thus avoided. The pure and physically homogeneous product exhibited the characteristic properties of natural IL-1β. The in vitro biological activity was measured in the lymphocyte-activating factor assay and was compared to that of natural IL-1β isolated from stimulated monocyte culture using exactly the same purification procedure. The specific biological activity of both products was 2 × 10−8 U/mg indicating that the recombinant product exhibits full biological activity