PRODUCTION AND CHARACTERIZATION OF RECOMBINANT CHICKEN INSULIN-LIKE GROWTH FACTOR-II FROM ESCHERICHIA-COLI

Recombinant chicken (c)IGF-II has been produced in Escherichia coli af ter first modifying a plasmid that coded for a human (h)IGF-II fusion protein. The cIGF-II fusion protein, deposited in bacterial inclusion bodies, was dissolved under reducing conditions, desalted, subjected t o anion-exchange chromatography and refolded. Recombinant cIGF-II was then released from the fusion protein using a genetically engineered s erine protease and purified to homogeneity by reverse-phase HPLC. In v itro analysis of recombinant cIGF-II revealed differences between cIGF -II and its human counterpart. Recombinant cIGF-II was less potent tha n hIGF-II in stimulating protein synthesis in rat myoblasts. This appe ared to be due to a decreased affinity far the type-1 IGF receptor. Th e human and chicken peptides were similar, however, in studies assessi ng binding to the type-2 IGF receptor and to IGF-binding proteins. Mor eover, recombinant cIGF-II and hIGF-II were equipotent in both biologi cal and receptor binding studies in chick embryo fibroblasts, suggesti ng that there may be a difference between mammalian and avian type-1 I GF receptors.