THE PRODUCTION OF AN ACTIVE PROTEIN-KINASE C-DELTA IN INSECT CELLS ISGREATLY ENHANCED BY THE USE OF THE BASIC-PROTEIN PROMOTER

Occasionally, only a small percentage of recombinant proteins produced in the baculovirus expression system are functionally active. We had previously shown that the majority of protein kinase C-delta (PKC-delt a) produced in insect cells was inactive; less than 1% of the expresse d enzyme had lipid-dependent kinase activity. In this report, we have attempted to optimize the production of a catalytically active PKC-del ta. Under optimum conditions, we were able to increase the levels of P KC-delta from 10-20% to about 65% of the total cellular protein; howev er, there was no increase in the levels of catalytically active enzyme . Expression of PKC-delta as a fusion protein or as a secreted protein also met with limited success. Under all conditions, expression of PK C-delta proteins under control of the strong polyhedrin promoter resul ted in the production of large amounts of inactive enzyme. Expression under the control of the basic protein promoter, P(cor), resulted in t he reduction of the levels of recombinant protein by a factor of about four, but the PKC-delta enzyme produced under these conditions was 10 - to 15-fold more active. Thus, the earlier temporal expression of PKC -delta in insect cells resulted in the production of more active enzym e. (C) 1994 Academic Press, Inc.