Differential Purification by Immunoaffinity Chromatography of Two Carboxy-Terminal Portion-Deleted Derivatives of Recombinant Human Interferon-γ fromEscherichia coli

Abstract

Two lower-molecular-weight derivatives of recombinant human interferon-γ (rIFN-γ) were purified concurrently from a lysozyme-EDTA extract of Escherichia coli cells by immunoaffinity chromatography using a monoclonal antibody (MAb) against a synthetic carboxy-terminal peptide (Lys-131-Gln-146). The two derivatives, 15K rIFN-γ and 17K rIFN-γ, were regarded to have been generated at the extraction step. They were successfully separated from each other by using another MAb against the same synthetic peptide with higher binding affinity than the first. The results of protein-chemical analyses indicate that 15K rIFN-γ and 17K rIFN-γ lack 15 (Arg 132-Gln-146) and 4 (Arg-143-Gln146) carboxy-terminal amino acid residues, respectively. All the data suggest that the two derivatives form a noncovalent dimer and that 15K rIFN-γ binds indirectly to the MAb column via 17K rIFN-γ.