Specificity of the immunoadsorbent used for large-scale recovery of interferon alpha-2a

After immunoaffinity chromatography, interferon alpha-2a synthesized in bacteria is not homogeneous. Beside oligomers and monomers, a fragment of molecular weight 15,000 was observed. Amino acid analysis and the determination of the amino terminal amino acid sequence of the fragment indicate that this polypeptide represents an interferon alpha-2a molecule lacking the 22 terminal amino acids. In order to define the epitope on the interferon alpha-2a molecule recognized by the immunoadsorbent, the binding to the immunoadsorbent of interferon alpha-2a fragments prepared by cyanogen bromide cleavage was studied. The results suggest that cyanogen bromide fragments Arg 22-Met 59 and Lys 112-Met 148 are recognized. Since the oligomers, the monomers and the fragment of molecular weight 15,000 of interferon alpha-2a share these sequences, the different forms are as expected co-purified on the immunoadsorbent.