Expression of a biologically active fragment of human IgE epsilon chain in Escherichia coli

cDNA corresponding to human IgE heavy (epsilon) chain mRNA was cloned from human IgE-secreting myeloma U266 cells. Partial nucleotide sequence analysis demonstrated that the cloned cDNA contained the coding region for about two-thirds of the CH2 and all of the CH3 and CH4 domains as well as the 3'-untranslated region. This epsilon cDNA was inserted into expression vector pUC7 and expression of an epsilon-chain fragment in Escherichia coli was demonstrated by protein blot analysis using 125I-labeled goat anti-human IgE as probe. The expression product was purified on a column of goat anti-human IgE-conjugated Sepharose 4B and the polypeptide was found to retain binding activity to human basophils.