The high-level expression of human interleukin-1β in Escherichia coli is described. The protein contributes about 12% of the total cell protein and is associated with the soluble cytoplasmic fraction of the cell. A method for the purification of the protein is given which is based on anion- and cation-exchange chromatographies. The isolated protein, shown to be homogeneous by several analytical methods, has been characterized by amino acid analysis, N- and C-terminal sequence analysis and analytical centrifugation. The protein is biologically active as demonstrated by two different in vitro assays, namely, the mononuclear cell factor (IL-1/MCF) assay and lymphocyte activating factor (IL-1/LAF) assay. The specific activities determined with the IL-1/MCF and IL-1/LAF assays, are 2 × 107 and 4 × 107 units mg−1, respectively.
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polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate
- IL-1/LAF assay
lymphocyte activating factor assay
mononuclear cell factor assay
combined gas-liquid chromatography/mass spectrometry
high-pressure liquid chromatography