CORRECT IN-VIVO PROCESSING OF A CHIMERIC UBIQUITIN-PROAPOLIPOPROTEIN A-I FUSION PROTEIN IN BACULOVIRUS-INFECTED INSECT CELLS

The cDNA coding for human proapolipoprotein A-I was expressed as a ubi quitin fusion under the control of the polyhedrin promoter in baculovi rus-infected Sf9 Spodoptera frugiperda insect cells. The fusion protei n was expressed at high level and was quantitatively cleaved in vivo. The cleaved product was purified and its N-terminal amino acid sequenc e was established. The data showed that authentic proapolipoprotein A- 1 has been produced, and thus demonstrated the existence in Spodoptera frugiperda insect cells of a specific ubiquitin hydrolase activity.