Expression and characterization of kinase-active v-erbB protein using a baculovirus vector system.

The v-erbB gene is an oncogene of the avian erythroblastosis virus encoding a protein that is a truncated version of the epidermal growth factor receptor. The v-erbB protein was expressed alone or as polyhedrin-erbB fusion proteins using the Bombyx mori nuclear polyhedrosis virus vector. The expression level of the fusion protein whose polyhedrin portion consisted of only 8 amino-terminal amino acids was more than ten times higher than that of the non-fusion protein. Studies with tunicamycin showed that the recombinant v-erbB proteins were glycosylated. The recombinant protein autophosphorylated tyrosine residues, and phosphorylated a synthetic tyrosine-containing peptide and lipocortin I. These observations indicate that functional v-erbB protein can be expressed in silkworm-derived cells, and furthermore, that this system can be used for large-scale production.