Synthesis of fusion and mature murine alpha interferons in Escherichia coli

Four murine interferon-α (MuIFN-α) genes (α₁, α₄, α₅, α₆) were previously identified and characterized. The coding regions of these IFN-α genes were inserted into bacterial expression vectors behind the lpp promoter under the control of the lac promoter-operator region, resulting in fusion peptides containing additional N-terminal amino acids (aa). Plasmids coding for the expression of mature IFN-α₁ and α₅ were also constructed using the same vector system, by inserting a 30-bp synthetic oligodeoxynucleotide, which contains a stop codon for the Ipp gene, a ribosome-binding sequence and an ATG start codon for the IFN peptides. The amounts of IFN polypeptides synthesized in Escherichia coli were estimated in the maxi-cell system and their biological activities were measured on mouse and other mammalian cells. The yields of mature IFN produced in this vector were 2 to 4 × 10⁶ units/liter; the antiviral activity of the majority of the MuIFNs on human and bovine cells was 100- to 1000-fold lower than on mouse cells. IFN-α₄, which contains an internal deletion of 5 aa, showed a lower antiviral activity than other MuIFNs on mouse cells.