Cloning and expression of an interleukin-1 beta precursor and its conversion to interleukin-1 beta

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