A BACTERIAL SIGNAL PEPTIDE DIRECTS EFFICIENT SECRETION OF EUKARYOTIC PROTEINS IN THE BACULOVIRUS EXPRESSION SYSTEM

Escherichia coli remains an organism of choice for the production of r ecombinant proteins required in large quantities. Whenever possible, s ecretion is the preferred strategy since it permits easy and efficient purification from the extracellular medium. Our efforts to use E. col i to secrete a human CD23 soluble variant fused to a pair of IgG; bind ing domains via the Staphylococcal protein A signal peptide were unsuc cessful. Surprisingly, when the same construct was expressed in the ba culovirus system, efficient secretion was observed and cleavage of the signal peptide occurred at the expected site. Varying the genes in th e fusions or the tags, or the topology of the gene and the tag, did no t affect the high-level secretion and cleavage at the correct site. We envision that fusion of the bacterial signal sequence to eukaryotic r ecombinant genes will prove to be a tool of value for efficient protei n secretion in insect cells using the baculovirus expression system. ( C) 1997 Academic Press.