High-Level Expression of Recombinant Bovine ß-Lactoglobulin in Insect Cells

Abstract

A cDNA coding for bovine β-lactoglobulin (β-LG) was obtained from a cDNA library constructed in λgt11 with poly(A)⁺ RNAs from mammary gland. The cDNA, although lacking 49 nucleotides of the 5’ end, was cloned into baculovirus transfer vector pVL1392 and inserted into the genome of the Autographa californica nuclear polyhedrosis virus (AcNPV) by homologous recombination. Cloned recombinant AcNPV was obtained by plaque purification, which was carried out by 3 rounds of visual screening of infected Spodoptera frugiperda cells (Sf9). For the production of recombinant β -LG, the cells were infected with the cloned recombinant AcNPV at a multiplicity of infection of 10 or 20. The level of recombinant β -LG in the supernatant was determined by sandwich ELISA. At 72 to 96 hours post-infection, secreted recombinant β-LG reached its maximum level. Correct processing of recombinant β-LG in insect cells was suggested, since the sequence of the N-terminal 20 residues was identical to that of natural β-LG. Preparative-scale production was performed by a suspension culture, the yield of recombinant β-LG achieved being 5 mg per 1 liter of the culture.

To whom all correspondence shouid be addressed