EXPRESSION AND CHARACTERIZATION OF HUMAN BONE MORPHOGENETIC PROTEIN-2IN SILKWORM LARVAE INFECTED WITH RECOMBINANT BOMBYX-MORI NUCLEAR POLYHEDROSIS-VIRUS

Recombinant human bone morphogenetic protein-2 (rhBMP-2) was expressed in silkworm larvae, and a milligram quantity of the protein was purif ied and characterized. The expressed rhBMP-2 was biologically active i n terms of induction of alkaline phosphatase activity in MC3T3-E1 cell s and ectopic bone formation in mice. On SDS-polyacrylamide gel electr ophoretic analysis, the purified protein showed a 16kDa band under red ucing conditions and a 30 kDa band under non-reducing conditions. The silkworm-expressed rhBMP-2 was glycosylated and susceptible to endo-be ta-N-acetylglucosaminidase F (endo F) and endo H, but resistant to end o D. Deglycosylated rhBMP-2 treated with endo F retained its biologica l activity. These results suggest that rhBMP-2 exists as a dimer and d isulfide bond(s) are responsible for the dimerization. Moreover, sugar chains have no direct effect on the biological activity of the protei n. The availability of a quite large amount of rhBMP-2 has allowed us to study the biological function of this interesting factor in detail.