Analysis of heterogeneity of gene products (interferon) expressed in yeast

FPLC, SDS-PAGE and Western blot techniques are used to analyse the heterogeneity of interferon alpha A (IFN-alpha A) expressed in yeast. The heterogeneity consists of (i) the presence of IFN polymer, (ii) partial processing of signal leader peptide and (iii) internal degradation. The reasons for heterogeneity of gene products in expression system of yeast are analysed. The methods of avoiding heterogeneity, such as depolymerization, adding inhibitors of protease to the culture supernatant, the oligonucleotide-directed deletion mutagenesis and improvements of fermentation, are discussed.