The baculovirus expression vector pBSV-8His directs secretion of histidine-tagged proteins

A novel baculovirus expression vector (pBSV-8His) directs secretion of recombinant proteins into the culture medium of infected insect cells. By providing a vector-encoded signal peptide upstream from a multiple cloning site, the product of the inserted cDNA is directed to the secretory pathway. In addition, a C-terminal His-tag allows convenient purification of the native protein directly from the culture medium in less than 5 h. The His-tag can be cleaved off the purified protein by utilizing an enterokinase cleavage site located directly N-terminal to the His sequence. By insertion of a coding sequence representing the human complement regulatory factor H-like (FHL-1) plasma protein into pBSV-8His, a high level of protein synthesis was demonstrated (9 micrograms/ml). The high level of production and the ease with which native protein can be purified almost to homogeneity, makes pBSV-8His particularly suitable for protein synthesis and purification. The combination of a vector-encoded signal peptide and a C-terminal His-tag allows production and direct purification of individual domains of secretory proteins in eukaryotic cells. This feature makes this novel vector extremely useful for structure function analyses of secretory proteins.